Update travis config to use rspec-puppet-augeas

https://github.com/domcleal/rspec-puppet-augeas
update documentation to include rspec-puppet-augeas
Improve Travis setup now includes:

- improved testing matrix
- excludin unsupported ruby and puppet version combinations
- syntax check for puppet 2.6.0
- syntax check for ruby
Exclude puppet module package directory with .gitignore
Merge branch 'rspec_augeas'