FIX keyword name
WIP fix type issues with sparse input
FIX type issues with sparse input matrices
FIX bugs with bootstrap / subsampling
ENH Better decision for switch algorithm in extract_nnz
Re-cythonize _tree.pyx and _gradient_boosting.pyx
ENH use proper semantic n_samples vs n_total_samples
FIX bug with treshold + ENH add RandomSparseSplitter
Re-cythonize _tree.pyx
FIX failing test due to type modification of X.data
Merge pull request #4 from arjoly/tree-sparse-imp3

Tree sparse improvement 3