add gemfile
add travis config
add build status icon to readme
use 'bundle exec' for build
work around PATH problems

use absolute paths to scripts when running tests
allow tests to use user-facing syntax
add comment around PATH munging
print out git version on travis
remove boilerplate comments from spec_helper
travis: display git version using before_script

don't override bundler installation
Merge pull request #13 from afeld/travis

set up Travis