Collection#find() can take additional args.

Newer version of pymongo added more args to find(). Most have no logical
effect.
Fix query qrray field with single value.

If a document has a field with an array e.g. 'x': [1, 2, 3], one should
be able to query for it with a simple query {'x': 2}.
Implemented $and and $or.
Check for Iterable not ListType.

This makes the code more general, and potentially Python 3 compatible.
Spell out timeout=True and not **kwargs.
Merge pull request #19 from 9gel/master

Fixed compatibility with pymongo 2.5 (Thanks @9gel!)
Add Database.drop_collection(...)
spec_or_id instead of spec