Google no longer recommends CONTRIBUTORS files for projects, since this
data is better retrieved directly from version control.

Additionally, contributors are now instructed to add themselves (or
their employer, if appropriate) to the AUTHORS file, rather than the
maintainers being responsible for trying to keep this file up to date.
Ultimately, this should result in more accurate data, since in most
cases we don't know whether the code is copyright the contributor or
their employer.

- simplify CLA text slightly
- clarify naming convention for .go files
- add "Maintainer's Guide" to document how I handle merging in
  contributions

mostly just typos and whitespace

Squashing is a little advanced, and easy to screw up with github pull
reqeusts.  If needed, I generally squash them myself anyway.