Moved barrier method example and added ConstrainedFunction version.
Bug fix in barrier example.
Print barrier solution information.
Scaling down barrier example.
Only print the first few dual variables.
Updates to ConstrainedFunction.

* Different stopping criteria.
* mu *= 2 instead of mu *= 100.
Remove linear programming barrier example.
to_string: only create one stream.
linear_programming: style fixes.
Wolfe line search with tests.
Readme update.
Wolfe line search bug fix.