MAINT: Update URL for free benchmark data.

Keep pace with Yahoo!'s change from ichart.yahoo.com to
ichart.finance.yahoo.com
MAINT: print function clean up in preparation for Python 3

- Use `print()` function for all print calls
- Fix strip and format calls that were on the outside of the
  print function for some reason.
  (Which were breaking in Python 3 because of print returning None.)
- Remove commented out print calls.
MAINT: Updated libraries

iso8601, pytz, numpy, python-dateutil, six, Cython, requests,

nose-parameterized, nose-ignore-docstring, scipy, matplotlib,
patsy

Note that patsy must install before statsmodels.
Fixes Issue 110 & Fixes Issue 108