UnicodeError with Python 3.4

Hi,

Today I've tried to run the Jedi test suite with Python 3.4 and found out that 7 tests were not passing. (I have uploaded the test reports on [this gist](https://gist.github.com/ColinDuquesnoy/9626362)).

The main issue is that Jedi does not open binary file in binary mode. This didn't show up until now because of #331, seems like the missing ```get_filename``` attribute of ```ExtensionLoader``` have been fixed for Python 3.4.

Note that there is still one test that fails for python 3.4, related to function signatures.

*I also added py34 to tox's envlist, not sure if can already do that for travis*