Add parameters to customize vmware-tools yumrepo.

Added yum_server, yum_path, just_prepend_yum_path, priority, protect,
proxy, proxy_username, and proxy_password parameters.
$just_prepend_yum_path allows the user to *prepend* an overridden
$yum_path onto the the default ./esx/latest/rhel6/x86_64/ path instead
of replacing it.
Rspec tests included.
Update README for yumrepo parameters.
Merge branch 'feature/yumparam' into develop
Update rake and Travis testing environment.
Increase puppetlabs/stdlib dependency to 2.3.0.
Update versions for 4.3.0 release.
Merge branch 'release/4.3.0' into develop
Use puppetlabs-stdlib 2.6.0 for testing.
Added manage_repository parameter.

Whether to allow the yumrepo to be manged by the Puppet module or out of
band (ie RHN Satellite). Addresses Issue #11.
Update README.md about manage_repository parameter.

Also switched from GFM for code snippets back to standard Markdown.
Updated README.md.
Fix Markdown code blocks in README.md.
Update versions for 4.4.0 release.
Merge branch 'release/4.4.0' into develop
Add CHANGELOG generation during module build.

Update the .gemfile to source gems from https://rubygems.org to fix a
Travis/bundler warning.
Update the Modulefile summary and description.
Minor changes to the README.md to clarify what the module is and does
and sync with the Modulefile description.
Update versions for 4.4.1 release.
Merge branch 'release/4.4.1' into develop
Update tests/init.pp to local standards.
Update .travis.yml to support updated Puppet versions.
Update Modulefile to use correct license name.