Added ParseBatcher class to execute batch create, update or delete operations with a single API call, including test cases and documentation. Also added ability to log in a user using Facebook or Twitter authorization.
Fix pip install command.
Merge pull request #18 from bitmole/master

Installation instructions
Altered count method to use count query rather than fetching all objects and finding the length
add master key header only if no user session is specified
Merge pull request #20 from joucle/enhancement

Add master key header only if no user session is specified
Merged with latest from upstream