Autodetect version of MythbuntuPPA for supported Ubuntu release

I've added a library to support the autodetection of the latest supported version of mythtv for any given release of Ubuntu.  The default recipe now uses this and the `apt_repository` LWRP from the [apt cookbook][1] to add the correct PPA.  This should work for all cases and fix an issue where `python-software-properties` was not already installed (and therefore `apt-add-repository` was not available).

I've also made significant improvements to the unit and integration testing framework for this cookbook.  Travis-CI is now available for use with testing changes to this cookbook.  If you'd like to add this to your repo,  simply follow steps 1 and 2 [here][2].  For detailed description of my changes see below:

Changes
=======

## v0.0.4

* Fix problems found in integration test suites due to long-running `apt-get install`s
  * Enable multiverse repo for dependencies
  * Adding `retry_delay` and `retries` params to frontend & backend recipes
  * Fix IOError (closed stream) & Mixlib::ShellOut::CommandTimeout due to long running apt-get commands
  * Removed unsupported centos-64 from test-kitchen platforms
  * Fix apt 404 errors by including mythtv::default & running apt-get update first
* Added serverspec integration tests for mythtv::backend and mythtv::frontend
  * Added default mysql passwd attributes for mythbackend test-kitchen suite

## v0.0.3

* Expand supported versions of Ubuntu:
  * Intelligently detect the latest version of MythbuntuPPA/mythtv to use based on LSB codename
  * Added MythbuntuPPA library (+rspec tests) for mapping supported platform versions to PPA versions
  * Use apt\_repository LWRP from apt cookbook to add the PPA
* Added cookbook test framework
  * Added chefspec, serverspec, test-kitchen tests (Run via: `rake` or `strainer test`)
  * Use knife cookbook test & foodcritic for linting
  * Use RallySoftware-cookbooks/cookbook-development cookbook test framework gem
  * Added more supported versions of ubuntu to test-kitchen platforms
  * Use [Travis CI](http://travis-ci.org) to automatically run tests for pull-requests & changes to this cookbook
* Minor enhancements
  * Fix metadata
  * Fix Foodcritic warnings: FC007, FC019
  * Cookbook version now specified in VERSION file


[1]: https://github.com/opscode-cookbooks/apt#apt_repository
[2]: http://about.travis-ci.org/docs/user/getting-started/