BUG: fix panel fillna ignoring axis parameter
added/fixed tests and re-ordered _is_mixed_type check
fill axis defaults to stat axis
implement inplace; simplify a bit
changed ffill and bfill default axis to None
fixed inplace implementation
added in @staple's tests
return explicitly for inplace
trying Panel.apply
more apply work
merge in new tests
simplify return
update tests with issue num and spacing before comments
added Panel4D.fillna suport and tests
added updates to v0.15.0.txt and updated fillna docstring
added issue numbers to v0.15.0.txt and added note for bug fix
more straightforward fillna method
fix panel4d tests
remove 'convert_numeric=True'