Added .screw_server.yml options support

Now a `.screw_server.yml` file can provide options.

Other changes:
* Updated bundler version to a more recent one.
* Repared specs, so they can run with ruby 1.9.
* Update version number to `0.1.9``.
* Fixed some typos
* Added travis support (see https://travis-ci.org/apepper/screw_server ).