Write speedup

[PointyShinyBurning]

Wraps up a few enhancements from our internal use of pandleau:

• Speeds up extract write (3-4 times faster on our internal workloads) by pre-calculating column set functions rather than a big elif chain on each value
• Adds tqdm progress bars to extract write
• Allows setting of table_name on extract
• Makes add_index create independent value rather than depend on input, avoids failure in case of e.g. multi-index or other non-integer-convertible index on input frame.
• Standardises formatting and deletes unnecessary (and .gitignore'd) output files from the repo

[bwiley1]

Wow these are great, thank you so much!!! I'll add your name to the authors list.