Start of some speeds up to soder.m.
Added the start of a test for soder.m.
test_soder.m works now.
Added a simple function for timing the Octave soder.m
Added a Soderkvist numpy function.

This is a highly vectorized version of the soder.m. It gives ~30X speed up to
the current Octave version. Computation for 60000 frames takes about 850 ms on
my machine as opposed to 25 seconds with Octave. The code is not producing the
correct results yet.
test_markers.py now passes.
Removed comment.
Merge pull request #27 from csu-hmc/soder

Improvements in speed and a test for soder.m.