added force memoize needs tests
force_memoize works properly, needs refactoring and readme
added force_memoize with tests and comments
Merge branch 'master' into stkomarov-fixes
force memoize with tests and comments
force memoize with tests and comments
added not NotInCacheError
removed key_override
added ignore_memoize attribute, removed unnecessary default_optional_kwargs, added clear_cache operation mode for memoize_query, fixed minor bugs
Merge pull request #8 from edx/stkomarov-fixes

Fixes issues with periodic tasks. Adds necessary functionality to memoize to interact with periodic tasks.