Some work on the bicycle example, added new notebook with new equations.
The bicycle example is closed to done.
Some updates.
More updates to bicycle example, almost done.
Added images for geometry and mayavi output.
Added images for geometry and mayavi output.
Many changes. I seem to have introduced another bug.
Change names of some measurement varibles.

The previous names created some confusion for me with common notation
for radii.
Merge pull request #2 from chrisdembia/jason-chris-bicycle-ex

[WIP] My edits on Jason's ipynb
Fine tuning, bug fixes, bicycle viz.

I fixed the bugs in the legs and most bicycle component locations. The
handlebar point is still incorrect. I also added some bicycle geometric
elements in the visualization.
Added Jason's measurements to check with another option.
Minor updates.
Some improvements to the visualization.
Fixed view image displays.
Clarification of limb lengths.
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.