break lines above 70 char's width

this is generally more convenient to read and to work on

tester/README.md

+
 ## Adding tests
-*(all paths and filenames mentioned in this section are relative to the `ext_tester` directory)*
-Tests are by expanding the code of the utility directly, using a provded API. The recommended way to do that is to declare and define a test-running function (i.e. a function that uses the API to run specific tests) in a my_test.h/c pair of files in the `executions` subdirectory, and then add a call to your function in the main function, located in `main.c`.   
-Don't heasitate to refer to the existing tests provided for a good example.  
 
-Before you go anywhere, your test file should include `../execution.h`  
-The core function of the test-running API is the `execute_test()` function. This function runs `mojitos` in parallel and takes a pointer to an `Execution` object that will define what is done with this run.  
+*(all paths and filenames mentioned in this section are relative to the
+`ext_tester` directory)* Tests are by expanding the code of the utility
+directly, using a provded API. The recommended way to do that is to
+declare and define a test-running function (i.e. a function that uses
+the API to run specific tests) in a my_test.h/c pair of files in the
+`executions` subdirectory, and then add a call to your function in the
+main function, located in `main.c`.  Don't heasitate to refer to the
+existing tests provided for a good example.
+
+Before you go anywhere, your test file should include `../execution.h`
+
+The core function of the test-running API is the `execute_test()`
+function. This function runs `mojitos` in parallel and takes a pointer
+to an `Execution` object that will define what is done with this run.
+
 ```C
 typedef struct {
-    char *const *args; 
+    char *const *args;
     Tester *testers;
-    int nb_testers; 
-    void *context;  
+    int nb_testers;
+    void *context;
 } Execution;
 ```
-- *args* points to a string array, which is the arguments that will be passed to `mojitos`.  
-- *testers* is an array of *nb_testers* `Tester` objects. Each of these objects defines a test performed during the run.  
-- *context* is an arbitrary pointer that will be passed to the testing functions.  
 
-The Tester object is defined as follows : 
+- *args* points to a string array, which is the arguments that will be
+  passed to `mojitos`.
+- *testers* is an array of *nb_testers* `Tester` objects. Each of these
+  objects defines a test performed during the run.
+- *context* is an arbitrary pointer that will be passed to the testing
+  functions.
+
+The Tester object is defined as follows :
 
 ```C
 typedef struct {
@@ -28,19 +43,32 @@ typedef struct {
     const char *name;
 } Tester;
 ```
-- *init*, *read* and *finalize* are pointers to function that will be called at various stages of the run. See below. 
-- *state* is an arbitrary pointer that may be initialized (to possibly allocated memory) by the *init* function.
-- *name* is a string that will be used in the output of the program.  
 
-The function pointers are defined as follow : 
+- *init*, *read* and *finalize* are pointers to function that will be
+  called at various stages of the run. See below.
+- *state* is an arbitrary pointer that may be initialized (to possibly
+  allocated memory) by the *init* function.
+- *name* is a string that will be used in the output of the program.
+
+The function pointers are defined as follow :
 
 ```C
 typedef void(*TesterInit)(void **state, void *context);
 typedef void(*TesterReader)(void *state, void *context, const char *buffer, int read_size);
 typedef int(*TesterFinalizer)(void *state, void *context);
 ```
-- The *TesterInit* function of a Tester is called once before `mojitos` is ran. It is given a pointer pointer to the state pointer, that will then be passed directly to the two other functions. Use this to allocate memory for a state-sotring structure. 
-- The *TesterReader* function of a Tester is called everytime `mojitos` outputs something. It is given a pointer to the null-terminated string that was read on mojitos output.  
-- The *TesterFinalizer* function of a Tester is called once `mojitos` exits, and should return 0 if the test failed (incorrect mojitos output), or a non-zero value otherwise. /!\ If this test uses a state object, it must be freed here !
 
-Notice how every function is also give a \**context* pointer. This pointer is the context property of the current Execution.
\ No newline at end of file
+- The *TesterInit* function of a Tester is called once before `mojitos`
+  is ran. It is given a pointer pointer to the state pointer, that will
+  then be passed directly to the two other functions. Use this to allocate
+  memory for a state-sotring structure.
+- The *TesterReader* function of a Tester is called everytime `mojitos`
+  outputs something. It is given a pointer to the null-terminated string
+  that was read on mojitos output.
+- The *TesterFinalizer* function of a Tester is called once `mojitos`
+  exits, and should return 0 if the test failed (incorrect mojitos
+  output), or a non-zero value otherwise. /!\ If this test uses a state
+  object, it must be freed here !
+
+Notice how every function is also give a \**context* pointer. This
+pointer is the context property of the current Execution.