0.5.2 release
- fix #48, use float variables in example GY521_test_1.ino
- add void calibrate(uint16_t times) to API
- add GY521_performance_calibrate.ino example
- add GY521_raw_cooked.ino example
- make explicit that pitch roll yaw is work in progress.
- update readme.md
- calibrate section
- add some tables
- minor edits in examples