Only run CI checks when appropriate files have changed

[brettcannon]

E.g. don't run code coverage or the test suite if only the docs changed (or vice-versa).

[berkerpeksag]

This is now done. @brettcannon could you please close this?

Side note: Should we allow "Core developers" team to close issues on this repo?

[brettcannon]

Closed and now the core team has write permissions (just simply forgot to add the team).

[brettcannon]

And thanks for the change! I'm sure not only PR submitters appreciate the faster turn-around but I bet Travis appreciates us using less free resources. 😄

[ammaraskar]

I don't think the Doc only test works. See this PR here: python/cpython#3072
The travis run: https://travis-ci.org/python/cpython/builds/263366915 (and it's console log)

It triggered a full code rebuild and test even though the only thing that has changed is Doc/library/socket.rst

[brettcannon]

It was working but it seems something has changed such that it didn't succeed in this case.