Add functionality to the 'New Game' button in the toolbar panel.

The 'New Game' button on the top of the window now spawns a new tab that has the window for creating a new Planning poker session. Currenlty only one tab can be opened, and the tab cannot be closed.
Merge pull request #29 from sfmailand/sbl-dev

Add functionality to the 'New Game' button in the toolbar panel.

So this is great, but I feel like Austin's interface that he used in the Overview tab would make sense in the new game panel, and a Requirement's Manager like list of games would be in the Overview tab.  Then we could have a small bar on the right with the options to fill out for making a new game or something.