(QENG-715) Add yard docs.

(QENG-715) Add new rspec tests.

(QENG-715) Give methods less generic names.

As pointed out in PR review, the use cases for these methods are pretty specific
and their names ought to reflect that specificity.

Signed-off-by: Wayne <wayne@puppetlabs.com>
(QENG-715) Remove old `install_dev_repo`

This method, rather than pushing repos to the SUT, has it pull from puppet labs
internal repository. This is deprecated by the newer
`Beaker::DSL::InstallUtils.install_dev_repo` which uses a push method.

Signed-off-by: Wayne <wayne@puppetlabs.com>