Structure for RPBI with permuted_ols_alt_chunk.

GrowableSparseArrays' return.
WIP: RPBI with parietal-python wards construction.
WIP: RPBI computation ends but h0 has a weird shape (lots of 0 and 'max').
Investigate parcellations mutual info.
Test RPBI with random parcels (Wards on noise).
Group by sessions in example.
RPBI: No dependance on parietal-python repository + improve DOC.
RPBI: More examples.
RPBI: Tests + Examples.
RPBI: complete tests.
RPBI: parameters in examples.
RPBI: Correct doctest for Travis.
RPBI: cosmit on examples.
RPBI: Change tests (even if seeded, order is hard to predict).
RPBI: cosmit in tests.
RPBI: Address bthirion's comments.
RPBI: address GaelVaroquaux's comments.
RPBI: more tests for normalize function + catch degenerated design.
RPBI: more refactoring + variable names.
RPBI: DOC (refactoring + description of RPBI).