Types: documentation, clean up, and testing

[chrisbolin]

BLOCKERS: Fix #61 and #62 in a beta release first.

• in the README document react-fast-compare's approach to typing: we need to support a huge variety of usages, and therefore the typing must be simple and should probably not be changed 😈. Reference all of the issues and PRs we've already had.
• while the Fix exported types so that they work for react-redux #61 fix is still in beta, direct users interested in types to that beta.
• make a github issue template. Explicitly mention types and direct the filer to the README documentation
• create TypeScript compilation tests that cover the issues/PRs we've seen so far
• ensure any other open issues are PRs are updated (probably closed) accordingly

Any of these can be made into separate issues to make tracking easier.