Added most of the docstrings to build_master_finders_table.py, what rema...

...ins unupdated needs to be refactored. For Ticket #136. Local tests failing due to a missing dependency. Should still pass on Travis.

This is a refactor of the code as well as a complete reworking of all the major docstrings. There is still more work to be done but this can be done in the parent `update-master-finders` branch.