Make Travis-CI work

These files will make Travis-CI work.
There are two steps to take before merging this pull request as outlined in [Getting Started](http://docs.travis-ci.com/user/getting-started/)
  - Sign in to https://travis-ci.org
  - Activate GitHub Webhook
    - Click on the switch for your repo on their dashboard

When this is set up, you can merge this pull request and Travis-CI should make a build, send you an email, and post to the IRC channel. This will happen every time a commit is done to any branch in the DoubleSha/BitcoinSwift repo, including master and pull requests.

The scheme files are needed because `xctest` and `xcodebuild` cannot automatically create schemes. This is currently the recommended way, and you can read more about it here:
  - https://github.com/facebook/xctool/issues/120
  - https://developer.apple.com/library/ios/recipes/xcode_help-scheme_editor/Articles/SchemeManage.html

I left out running the unit tests because they currently don't work. There's currently issues with the simulators on Travis-CI.
  - http://status.travis-ci.com/incidents/y9pysslbxb79