Added specific errors for most validation errors
Increased test coverage by a tiny bit...
Changed comments to docstrings
Added fix for custom messages error throwing.
Added fix for custom messages error throwing.
added Remove marker and new extra keys treatment option
add COPYING to build artifact. Fix #80
Merge pull request #83 from ngmiller/add_copying_to_tar

add COPYING to build artifact. Fix #80
fixed the Msg error and added more Invalid subclasses to handle Is* functions
updated mapping sort priorities to avoid clashes between remove and other schemas
added more Remove tests
Merge pull request #82 from sirfz/add_remove_capability

Add Remove marker and option for extra keys to be excluded from output
Merge pull request #81 from bdejong/master

Added specific errors for most validation errors
updated compiled mapping sort and moved candidates computation to outside of validate function
set Remove as hightest priority Marker to avoid conflicts
revoked accidental doc deletion
Merge pull request #86 from sirfz/improved_map_sort

Improve Mapping Sort and Moved candidates Outside validate_mapping()
Don't allow construction of dict/object schemas with duplicate keys

Inadvertently creating a schema with both Required and Optional versions
of the same key creates indeterminate behaviour, so disallow.
Don't put keys to be removed in keys_set