add travis build status to README

http://about.travis-ci.org/docs/user/status-images/#Adding-Status-Images-to-README-Files

http://about.travis-ci.org/docs/user/status-images/#Build-Status-For-Specific-Branches
rearrange README sections

* clarify at top that this is a canary test for rspec-hiera-puppet
* move travis-ci build status to top
add basic CONTRIBUTING.md