Improve the selection of the steer and roll rate gains.

[moorepants]

Mont and I talked about this and think that we can use fsolve to simultaneously find the gains for steer angle and roll rate that ensure the closed loop polls of the roll rate loop have a frequency of 10 rad/s and damping ratio of 0.15 (10 dB peak).

[moorepants]

Even better, it is possible to solve for them analytically: http://nbviewer.jupyter.org/github/moorepants/BMD2016/blob/master/notebooks/solve_inner_loop_gains.ipynb