build IMU checkout function

[jacobrdavis]

Build imu.checkout(), a function within the imu.py submodule which initializes, runs, and diagnoses the IMU module. Some ideas:

• turn on and initialize the IMU module
• run the IMU module for a short period of time (e.g. one minute) using the recordIMU.py function
• confirm that the test data contains all of the expected fields and are uniform in length (and close to what is expected based on the sampling frequency and record length)
• check the test data to confirm the data is not
• record the biases of the accelerometer and gyroscope fields; return these to the user for calibration (or directly write them to a calibration file?)
• confirm the specified sampling frequency matches the sampling frequency set by the user with the config file (from the data and by checking the IMU module settings)
• check acceleration G limits and confirm they match the config file
• check the accelerations and gyroscope readings close to zero (for a stationary test) (using the recorded biases?)
• create a sub report describing the module's performance and any diagnostics suggestions, then return it to checkout.py?

There may be some preexisting tests in the couldbeuseful/ directory that can be reused; see imu.record() and the IMU module documentation for interfacing with the IMU module itself.