Allow to use custom python interpreter [fixes #339]

Author: st4lk

setup.py

@@ -35,7 +35,7 @@
         'configparser; python_version<"3.0"',
         'future>=0.14.0',
         'futures; python_version<"3.2"',
-        'jedi>=0.12',
+        'jedi>=0.13',
         'python-jsonrpc-server>=0.1.0',
         'pluggy'
     ],