Brought to PEP-8 and used proper path joining.
Brought filldb.py to PEP-8, removed extraneous imports and small changes to variable names to be more expressive.
Fixed error with a mutable default argument. If it ran twice, it would duplicate tags.

Also brought up to PEP-8, yadda yadda.
Updated mapthread_downloader to be mostly PEP-8 compliant. A few small changes to simplify the logic.
Added requirements.txt
PEP-8 fixes.