Update .gitignore to exclude the Leap SDK files, but not the stub header
Merge pull request #591 from machinelevel/dev

Update .gitignore to exclude the Leap SDK files, but not the stub header
Hand rework in preparation for adding send/receive hand data
- Added Hand.cpp, Hand.h, HandData.cpp, HandData.h, roughly matching the equivalent Head files
- Cleaned up Avatar by moving hand work into Hand files
- Added fixed-point data packing, for use in sending hand offsets
Networked Leap fingers
- Simplified finger updates and storage
- added pack and unpack for the fingers
- not yet tested between multiple machines, but *should* be harmless and backward-packet-compatible
Merge pull request #592 from machinelevel/dev

Hand rework in preparation for adding send/receive hand data