Added instance weighting to searn sequence task.
Support searn through the library interface.
Update searn so that finish_example is only called when used with drive.
Merge pull request #146 from akhudek/master

Searn example weighting and library interface
fixed audit for gd_mf
fix reference
Merge branch 'master' into save_best
printout tweak for gd, bfgs, oaa
finish coding all reductions
update test cases