* Allow extra runtime deps to be defined when using prune_bundler
* Check extra_runtime_dependencies is set before iterating over them
* Load additional paths for extra runtime dep gems
* Don't load extra dependencies, just add their paths to $LOAD_PATH
* Fix typos and extraneous checks and rescues
* Use Gem::Specification#full_require_paths when available
* Prevent use of prune_bundler and extra_runtime_dependencies with early versions of RubyGems
* Ensure LOAD_PATH is modified by extra_runtime_dependencies
* Refactor prune_bundler in launcher.rb and write some unit tests
