Merge pull request #438 from doubleday/master

- Fixed assert for tween action callback case
updated and changed license.
Update Readme.md
latest monogame
Made the selector more type specific, and added events to handle the menu item actions.
more specific typing of the selector for menu items.
Some safety checks for NRE
Fix for single word label not drawing properly.
Added the threading support methods from MonoGame so that some tasks can run on the UI thread. This is useful for doing IAP actions on Windows Phone.
fix for build error
fix for broken build
fixes for threading method scope
removed unneeded project files
- Update CCLabelBMFont in visit instead of draw to prevent 'jumping' when changing the text