Release the GIL at tree building time
Put more code under non-GIL block
MAINT remove mlcomp document classif. example

It's redundant given the other 20newsgroups example.
Merge pull request #2528 from ogrisel/tree-nogil

[MRG] Release the GIL at tree building time
Add implementation of RANSAC algorithm
Add ransac function to __init__.py of utils package
Fix bug in residual determination
Add step-by-step description of RANSAC algorithm
Add parameter description to RANSAC and modify API
Add example plot script for RANSAC
Add simple RANSAC unit test
Add unit tests for RANSAC is_model_valid and is_data_valid
Add unit tests for RANSAC max_trials option
Return number of trials in RANSAC
Fix n_trials return value and add additional test
Add n_trials return value to doc string
Add test for stop_n_inliers parameter
Add test for stop_score parameter
Move ransac.py to _ransac.py to avoid nosetest namespace conflict
Set numpy random seed for all test functions