Remove Python 3.2 from .travis.yml (python#444)

Our `setup.py` file explicitly throws an error when users try and
install typing for Python 3.0 through 3.2. In that case, it doesn't
seem like testing typing against Python 3.2 is worth it.

.travis.yml

@@ -7,7 +7,6 @@ python:
   - "3.5"
   - "3.4"
   - "3.3"
-  - "3.2"
   - "2.7"
 
 install: