Updated Gemfile with rake, no specific version

Signed-off-by: Byron Sanchez <bfs5030@gmail.com>
Updated input markdown file component

Instead of individually defining which files to process, each .md file
in the markdown directory will now be processed and the output will be
placed in the output docs directory.

Signed-off-by: Byron Sanchez <bfs5030@gmail.com>
Packaged rake gem in the cache

Signed-off-by: Byron Sanchez <bfs5030@gmail.com>