Enhance the README text
Enhance the contribution document
Change minor phrasing in the API docs.

Also cut lines at 80 chars.
Factorize some verification code
Add better comments in the code.
Put code blocks inside {}
Remove the internal storage of tokenId and authKey in the token.

Because the operation to generate them is async, it doesn't really make sense
to have them inside the object itself.

Having one API to get them seems simpler to deal with in the future, and avoids
future possible confusion (say people trying to use these values when they
don't exist yet).
Use sentences everywhere (starting with a caps and ending with a dot)
Merge pull request #36 from mozilla-services/enhance-contributing-docs

Enhance the contribution document
Merge pull request #35 from mozilla-services/readme-enhance

Enhance the README text
Merge pull request #37 from mozilla-services/enhance-api-docs

Change minor phrasing in the API docs.
Merge pull request #38 from mozilla-services/rework-token

Remove the internal storage of tokenId and authKey in the token.
Better docs
Merge pull request #39 from mozilla-services/minor-changes

Minor changes
Fix #32 — Implements MOMT protocol for Nexmo.
If we cannot send the sms, raise a 503 error to let the client try again.
Improve docstring.