Create functions for customization

[vsoch]

The snakemake interface (snakeface?) will likely have the ability to customize configuration files and recipes. If there are standard files, or perhaps even if the user wants to customize a snakemake-wrapper, there should be an easy function that takes a repository, finds the file of interest, and then makes it easy to edit it (without some custom parsing). Likely I'll develop this as I start snakeface and the actual need comes up.