Benchmark: use default values in forests
WIP: remove irrelevant and unstable doctests
WIP: address @ogrisel comments
WIP: address @ogrisel comments (2)
WIP: remove partition_features
WIP: style in _tree.pyx
WIP: make resize a private method, improve docstring
WIP: use re-entrant rand_r
FIX: doctest in partial_dependence
WIP: break or shorten some long lines
FIX: doctest in feature_selection
WIP: break one-liner if statements
WIP: revert use of rand_r
ENH back-port rand_r from 4.4BSD

This function is not available on Windows and is deprecated by POSIX.
Fetched from OpenBSD:
http://www.openbsd.org/cgi-bin/cvsweb/src/lib/libc/stdlib/rand.c

This reverts commit 6f737ad8d5b29a098df6b2ad0fdd1db38e801db8.
FIX move rand_r to tree module for now

Simple build and link without an intermediate Cython module.
FIX: broken tests based on rng
DOC: update header in rand_r.c
TEST: skip test in feature_selection (too unstable)
FIX: one more doctest
WIP: Faster predictions if n_outputs==1