[setup.py] Update setup.py to install Cmake lib in python env by default.

Update setup.py to install Cmake lib in python env by default following PEP405.

README.md

@@ -6,16 +6,19 @@ You can find here the C++ code of the Core library of Aidge.
 
 ## Pip installation
 
-To install aidge_core using pip, make sure to set the desired install path :
-``` bash 
-export AIDGE_INSTALL = '<path_to_aidge>/install'
-```
 
-Then run in your python environnement :
+
+To install aidge_core using pip, run the following command in your python environnement :
 ``` bash
 pip install . -v
 ```
 
+**Note:** you can specify a custom install folder by setting an environment variable:
+
+``` bash
+export AIDGE_INSTALL='<path_to_aidge>/install'
+```
+
 ## Standard C++ Compilation
 
 Create two directories ``build`` and ``ìnstall``.