(maint) rename spec files

The common convention for naming spec files is ${tested_file}_spec.rb,
and running the `rspec` command will run all accordingly named files.
This commit renames all existing spec files to conform to this
convention.
(maint) simplify rspec spec_helper.rb require

With rspec 2 simply doing `require 'spec_helper'` will bring in the
project spec helper. This commit removes the existing complex require
logic with a simple require statement.
(maint) use 2 space indentation for spec files

All of the spec files were using 4 space indents. This commit changes
the indentation to the standard 2 space indent that's the common
convention in the ruby community.
(maint) add Gemfile

This commits a basic Gemfile to allow for easier testing. It respects
the environment variable 'PUPPET_GEM_VERSION' in cases where the module
needs to be tested with multiple versions of Ruby.
(maint) add .travis.yml configuration

This commit adds configuration for travis-ci to test this module against
supported versions of puppet. It also suppresses emails on
travis builds.
Merge branch 'maint-cleanup_spec_files'

This closes GH-21 and GH-22