Update travis to 3.5 (instead of 3.5.0.rc4)

.travis.yml

@@ -1,7 +1,7 b''
 # http://travis-ci.org/#!/ipython/ipython
 language: python
 python:
-    - "3.5.0rc4"
+    - 3.5
     - 3.4
     - 3.3
     - 2.7