Added Database.create_collection method.
Merge pull request #115 from marcinbarczynski/master

Added Database.create_collection method.
Acknowledgements
Merge pull request #117 from tipok/master

Fixed drop collection functionality and added drop database functionality
Acknowledgements
Merge pull request #118 from tipok/master

fixed find by document value
refs #114: Added alive method to Connection

This method is pretty basic. Normally it would check it can open a
socket to the server. As there is no server (we are mocking it), it
simply returns True.
Merge pull request #119 from pacud/master

refs #114: Added alive method to Connection
Acknowledgements
added dereference
new line at the end
Merge branch 'master' of https://github.com/tipok/mongomock

Conflicts:
	mongomock/database.py
	tests/test__mongomock.py