Remove some functions from the API
Small post v2.15.0 fix in check_keys
More consistent API and other things (see CHANGELOG)
add check_df to API again
small fixes to follow up on v2.14.0 - see CHANGELOG
Only V2 funcs can be used if env var set - see CHANGELOG
improve docs + bugfixes -- see CHANGELOG
Small improvements: See CHANGELOG for more details
Big update to pythonwhat: See CHANGELOG for more details
tiny messaging fixes