v0.3.0

• overwrite now takes an enum Overwrite (backported to 2.7 via enum34) with values NONE, PRIMARY, SECONDARY, or ALL instead of string values (though the implementation is backwards compatible to using the old string values).
• copy.copy() and copy.deepcopy() now work properly on a MultiDirMap
• aslist() and asdict() on row elements renamed to to_list() and to_dict()
• new method to_list() which returns complete map data as a list of lists