Add .travis.yml CI config
Remove pry as a gem dependency

As we're building on Travis, we should be minimizing gems installed in
the test environment. Furthermore, pry is a developer preference, not a
dependency for development.
Add Travis build status badge to README
Include development dependencies in CI install

As we mark cucumber as a development dependency in the gemspec (and we
gemspecs don't support test dependencies) we have to ensure we bundle
install everything, otherwise we can't run cucumber. D'oh!
Merge pull request #65 from mdsol/feature/configure_for_travis_ci

Configure for Travis CI