Proper Readme about tax-calculator

[iliakur]

@MattHJensen here's something we could do: if we're working on resolving an issue, we could post our commits in the issue's thread so that a) there's record of some progress in case we get distracted and have to put it on the back burner and b) so that people can maybe discuss this progress in its intermediary stages.

For instance, I'm going to link to your most recent commit on this topic like so:
55e74a9

The easiest way to grab a commit link is by going to the repo's home page, then clicking on "commits" under the repo name. You'll see a list of commits and to the right of them buttons that allow you to copy a commit's hash code into your clipboard. You then simply paste the commit hash into your message here and it will appear as a link.

[MattHJensen]

Sounds good. Thanks.

[talumbau]

I like the idea of text in the README that describes how to get started. I think a good goal would be to have these sections:

• Installation (maybe with a couple of options)
• How to run the tests
• Links to relevant sites

[talumbau]

we have progressed beyond a README. Closing in favor of other issues to discuss doc needs.