Add gitignore

Change-Id: I9fc0826ef5bd0049b8d5313302a85b718de95ec3
Calculator: New Features Part 6

- Floating Calculator
- New theme engine (& store)
- Google Glass support
- Graphs rewritten from scratch to support equations such as circles
- Panels can be rearranged
- Infinite scrolling option
- Details in top left. Quick toggle for Radians/Degrees
- Button vibration option
- Widget UI updated to match stock apps
- Settings cleaned up
- Code cleanup

Change-Id: Id096d35b854833044f7168e7a16cd95f8ef8bbd1