setting up compose for tracks

Updated the `compose.cwd` to point to the releases folder. This needs to be relative to the Gruntfile since it doesn't take into account the `cwd` set in the `files` property.

Added `tracks` property to the `A/index.html` and `B/index.html` YFM to point to their tracks folder (ideally it would be  nice to get this dynamically, but I don't see a way to do it yet.)

Updated the `src` parameter to `compose` to use the `tracks` property in stead of the hardcoded string.

The `tracks` property can be updated to be whatever you like in case of a conflict (eg... `tracksPath` or something)