Update INSTALL

Updated the Mac, Linux & Unix section. Easy install no longer work, Pip should do.

Author: mahveotm

INSTALL

@@ -11,9 +11,10 @@ Installing ebaysdk on Mac, Linux, Unix:
    Ubuntu:
    sudo apt-get install python-lxml
 
-2) Install the SDK with easy_install
+2) Install the SDK with pip
 
-   sudo easy_install ebaysdk
+   python3 -m pip install ebaysdk
+
 
    Or install the latest version from github,