Integrate Object Defintions

This pull request represents the definition of core domain objects including UserStory, Task, Sprint, and Iteration. These objects are mappable and persist through a preliminary sqllite file based database.

Resolves #14 
Resolves #13 
Resolves #9 

/cc @cupcakesrrad @Sperovita 

If you guys are ready to try some UI integration we can postponed this pull request. It would be easier to get your work integrated into dev then I can rebase and get db into dev after that than it would for db to go first.

Ultimately, I want to get some commits ready for demonstration for the presentation on Friday. We can all approve these pull requests, but I think understanding and discussion is necessary if time permits.