fix 2-level glm implementation and move it to nipy.algorithms
re-implement parcel-based group analysis method (Keller et al, Statistica Sinica 2008; Roche, OHBM'12 talk)
account for Bertrand's PR review
remove old parcel-based group analysis code from labs
Account for Matthew's PR review
increase test coverage
raise test coverage to 92%
raise test coverage for parcel_analysis.py (99%) and bayesian_mixed_effects (100%)
Merge pull request #292 from alexis-roche/refactor-group-analysis

MRG: Refactor group analysis

A fast re-implementation of the parcel-based group analysis method proposed in Keller et al (Statistica Sinica 2008, MICCAI 2009); moving implementation from nipy.labs to nipy.algorithms.