added --dropnulls and --dropzeroes options
updated docs for --dropnulls and --dropzeroes
combined options --dropnulls and --dropzeroes to --drop {nulls,zeroes}
added --drop empty option
added --drop empty docs
fix write optimization in update_many
reduce len calls in update_many
--drop flag may only be specified once
reverted setup.py and .gitignore
removed unneeded assertion
replaced itertools.ifilter call with list comprehension
Merge pull request #57 from coderfi/master

added --dropnulls and --dropzeroes options to whisper-fetch.py
New whisper-fill utility.

Backport from https://github.com/jssjr/carbonate/

Fixes #22.
Merge pull request #88 from deniszh/master

New whisper-fill utility.
Merge pull request #81 from timob/fixupdatemany2

fix write optimization in update_many