Fix _nbsp after contains() semantics change
Fix _warn_extra_opts after keys() change

(thanks @simonster)
has->contains for Sets

(thanks @simonster)
Fix search(::String, ::Char)

(thanks to @maleadt)
has->haskey in ArgParseSettings
Add tests
Small fixes

* avoid using dest_name for pos_arg commands
* remove auto-added help/version in case of errors
Bump version to 0.2.2