typo on PUT_MANY
Merge pull request #300 from justinwp/patch-3

typo on PUT_MANY
Prepares for version 0.13.0 release.
Bump version number to 0.13.0
Set development version number to 0.14.0-dev
Output exception message if value is compared to NULL in search.
Test case for comparison to NULL with generic operators.
Fixes typo in docstring.