failing imu unit tests

[RussTedrake]

pull request #274 almost resolves this one, and will soon. but the planar kinematics of the IMU are still known to be broken.

<matlab_test>~isempty(strfind(error_message,'bug 1728'))</matlab_test>

[RussTedrake]

for reference, those list of comments are mostly from our original github integration scripts, which added a comment every time the known issue was triggered by the build server.

the planar manipulator dynamics methods in matlab are now simply running the 3D dynamics engine and projecting all of the relevant quantities down into the 2D space. during that transition, we never quite finished fixing the IMU projections (since they weren't being used in anything on the critical path). would be good to resolve, but is not high priority.

[RussTedrake]

won’t fix (matlab only)