Add Travis status to README

Also cleans up some formatting in the README
Make code pass puppet-lint

Without this commit, the code would not pass the puppet-lint in Travis.
Merge pull request #4 from ghoneycutt/fix_lint

Make code pass puppet-lint
Merge pull request #5 from ghoneycutt/README_fix

Add Travis status to README
Use domain fact as the default value for domainname param

This will give a better default than example.com
Merge pull request #7 from ghoneycutt/use_domain_fact_for_default_value

Use domain fact as the default value for domainname param