Move several useful utility scripts into a top-level "contrib" folder

[johndgiese]

After having used RDM on several client projects, we've accumulated a number of python scripts and other files that may be useful to others. Many of these won't be useful on every project, thus we aren't going to directly integrate them into init_files. That being said, we should document them and include them in a top-level contrib folder.

Here are a few scripts to add:

• [x] @russellkan 's script for parsing Debian dependency files: https://github.com/innolitics/rdm/pull/87
• [x] @ReeceStevens 's GitHub action for compiling everything
• [x] The basic requirements.txt -> requirements.yml script
• [x] The merge requirements script

For each of these we should clean up the file, write some documentation, and add a reference to it in the README.