Avoid redirecting stderr with ipython qtconsole

Closes issue #3.
be a little smarter about when to redirect stderr

The fix in 0e34978 doesn't work in the most recent versions of
IPython.
Merge pull request #4 from dougalsutherland/fix-stderr

be a little smarter about when to redirect stderr
use different random seed for each invocation by default
always restore stderr, even if there's an exception in run()
Add basic documentation for optimizing()
Merge pull request #6 from dougalsutherland/always-unredirect

always restore stderr, even if there's an exception in run()
Merge pull request #5 from dougalsutherland/random-seeds

use different random seed for each invocation by default
handle return parameters correctly in optimizing()
Add a test to catch row-major/col-major indexing problems
Merge pull request #7 from dougalsutherland/optimize-pars

handle return parameters correctly in optimizing()
Fix for optimizing
Test for optimizing returning matrix
Fix _par_vector2dict's handling of Stan's column-major ordering
Carefully squeeze (1,) arrays into scalars
Add very simple test of optimizing
Improve clarity in _par_vector2dict
Add __str__ and summary methods to fit objects

Just as in RStan, printing a stanfit object will print a summary that includes
summary statistics for parameters of interest.

Estimated sample size and Rhat are not yet included in the statistics.
v0.2.0 release