Added sketch to test ESCs/motors independently
Added MPU6050 digital low pass filter configuration
Fixed bug in which initial attitude may not be (1, 0, 0, 0)
Handle IMU loop time as a float rather than a uint32_t
Added angles (roll, pitch, yaw) calculation to IMU library
Use time in PID calculations
Added function to reset PID calculations
Read serial device and speed from command line arguments
Added initial quadcopter sketch