Update travis config file

This commit standardizes the Gemfile and travis.yml to be similar
to the files in stdlib. Puppet 3 and ruby 1.9.3 are now added to
the matrix
Merge pull request #148 from blkperl/update_travis

Update travis config file
Fix a typo in database_user.rb
Merge pull request #150 from camptocamp/master

Typo
Solve an edge-case of syntax highlighting in README.md

In my vim-setup, the underscore in `create_resources` leads to
rendering everything in italics after that. Wrapping it in backticks
solves this in the editor and also looks better when rendered as HTML.
Merge pull request #152 from kronn/patch-1

Solve an edge-case of syntax highlighting in README.md
Fix tests for Puppet 3.0 target
Fix issue with twice declaration of Database_user resource
Merge pull request #154 from Paulche/master

Fix issue with redeclaration of database_user via mysql::db