Fix Travis in several ways

[delcypher]

This PR does the following:

• Makes the right Python version be used in each configuration.
• Run the unit tests in TravisCI
• Run the wllvm-sanity-checker during testing to check it can be executed.
• Fix wllvm-sanity-checker to work under Python 3
• Disable testing Python 2.6. I don't know how to run the unittests for that Python version.
• Add testing for Python 3.4 and 3.5.

@ianamason You'll see I've added a pip --version command. In Travis if you look at the log for each Python configuration you'll see they show different output. So now we can see that the intended python version is being used.

I'm not sure if you needed Python 2.6 support but I can't run the unit tests under that ancient version.

[delcypher]

@ianamason Okay this ready for you take a look at now.

[ianamason]

Thank you for this Daniel.

I have never knowingly used 2.6 so ...

I'll merge and push the pip now.

[ianamason]

1.0.17 is live on pypi so if you wanna give it a burl, I can then close the issue. Again thanks.

[delcypher]

@ianamason 1.0.17 is working fine. I've closed the issue noting the commits and PR needed to fix the issue.