Change symbols for handlebar solution.

I was using d_rx, etc. previously. However, these quantities are
MEASURES, meaning they can be negative. The use of `d`, at least to me,
seemed to indicate that these were distances that were necessarily
nonnegative. So I chose to use greek symbols. I wanted to use `m`, for
measure, but I think that could be confused for mass.
Fix bug in front view.

The mayavi image labeled front view was previously a rear view. The
handlebar circle should be at the left hand, and so should be on the
right in a front view.
Add comforting note about the optimizer's warning.
Reorder handelbar bicycle unknowns for consistency.
Fix bug and misc.
Merge pull request #3 from chrisdembia/jason-chris

Fix the numerical bug that was causing the handlebar location to be incorrect.