docs(standards): add commit style guide

this introduces a new commit standard for Deis developers. The
goal of this commit is to allow developers to search through
the history better, provide us better information through
commit messages, and eventually allowing us to script the
CHANGELOG.md so that we do not have to rely on a third-party
tool to do the parsing for us.
docs(standards): update old commands

some of the documentation's listed commands are outdated and need
to be updated to reflect the new workflow changes.
docs(standards): use proper english

Some of the sentences in the documentation is poorly written.
Merge pull request #680 from opdemand/add-contributing

docs(standards): add commit style guide