Bugfixes and new features, matches underscore.js v1.6

v0.1.6

Fix key error problem and add tests #11

Python 3 Support

Thanks to @jiaweihli underscore.py now supports both python 2 and 3

Latest Stable

Implements new methods from underscore.js

ADD: where, findWhere, pairs, invert, partial, indexBy and random
ADD: tests for these new methods
FIX: return object instead of list if there is only one item groupBy
FIX: timing on async tests

Stable version

Used new classes for python