gitignore: add "coverage"
FIX: make_inverse_operator checks

don't assume that loose=None entails fixed=True
ENH: parameters for make_inverse_operator

automatically set loose = None for fixed = True, but issue warning if loose
is not None
ENH: make_inverse_operator

Allow surf_ori=False forward operator with loose=1
TEST: add test_make_inverse_operator_free()
RF: compute_orient_prior; pep8
DOC/error messages

 read_inverse_operator parameter checking