travis-cargo no longer works with coveralls, and appears
to be unmaintained. This change use regular cargo to
build and test. It now uses cargo-travis to push test
results to coveralls. This will also build nightly, and
only push test results on the stable build.
* Use docs.rs for documentation
This would also allow deleting the `gh-pages` branch (which is pretty large).
I'd also recommend adding `badges` and `categories` to make the crates.io page more useful (see [this](http://www.integer32.com/2017/01/20/categories-and-ci-badges.html)), but I'll leave that up to you.
* Remove more references to old docs
