Decrease errors found with cpplint down to zero
tools: Add script for coding style checking

For now it should be enough to remember ourselves to run this script from time
to time. I think we'll get used to this habit. Later we can think in a
pre-commit git hook or something to enforce that all developers are running it:

http://stackoverflow.com/questions/3462955/putting-git-hooks-into-repository

Fixes #91
Add OWNERS file for tools/
Style: Ensure includes are in alphabetical order.
Tools/cpplint: Enable all error categories as we pass all of them.