Fix checking rate_limit_status for Twitter 1.1

Note that the call to `rate_limit_status` now
gives remaining hits for each API endpoint.

See the [rate limiting
documentation](https://dev.twitter.com/docs/api/1.1/get/application/rate_limit_status)

This fixes #5.
Merge branch 'master' of github.com:jonathansick/astrotweet