Fix #215: Helper for int and double now work as expected.
Pinned protobuf at >= 2.5.0.

See discussion on Issue #215 for details.
Updated naming of global variable to follow PEP8.
Always cast int and long values to a long when preparing for a request.
Merge pull request #216 from jgeewax/master

Fix #215: Helper for int and double now work as expected.
Removing pylint statements in datastore.entity.

Adding a pylint plugin to suppress the maybe-no-member
statements when type inference fails.