Merge pull request #1052 from dengemann/mpl_maint

ENH/FIX/MAINT: add back support for MacOSX backend in mpl
ENH: add field line viz function and method
remove contains experiment
API : refactor the plot_evoked_field function
API : name it make_field_map
add some comments
fix test
fix test
API : refactor plot of field maps (make make_surface_mapping private)
update test_field_interpolation
TST : add test for field viz
keep n_jobs in examples
API : add plot_field method to Evoked
wining 20s of test time + pep8 in viz.py
FIX : make it work on CTFs systems + demo the feature on SPM data
misc what's new
FIX : make test pass without sample data
misc
FIX : tests should pass now...
MISC : check ch_type + update docstring