(maint) Update invoke_task to support passing multiple arguments

Previously the invoke_task method was limited to passing 0 or 1 argument
to the rake task. It is occasionally desireable to pass more than 1
argument, so this commit updates the method to take an arbitrary # of
extra arguments, and pass them on to the Rake::Task invocation.
(maint) Update rm_rf call in file_spec to use FileUtils
(CPR-52) Add deploy_nightly_repos task

This commit adds a deploy_nightly_repos task which will be used to ship
the signed nightly repos to the public nightly repository. It retreives
the repos and repo_configs and then swaps out the distribution server
for the nightly server, to ensure that the repo configs are functional.
This task also creates a latest symlink for the project.
Merge pull request #324 from haus/ticket/master/cpr-52-nightly-repos

(CPR-52) Add deploy_nightly_repos task