Some revisions to clarify contractor work.

When the document discusses the terms of work of 18F's contractors,
it should be understood that this policy commits 18F to negotiate
contracts that ensure those terms. It is not meant to imply that
these terms apply to contractor work government-wide.
Updates!

-Removed the Legal and Policy section
Merge pull request #11 from 18F/final-revisions

Resolving final comments