First production release!

Bumped to v1.0.0 since "all" features are now added! (I.e. The gem is no longer in development.)

The main change since the previous release is a big refactor of char group parsing, which fixes some bugs and allows the use of set intersection - for example the following now work:

/[[a][b][c]]/.examples # => ["a", "b", "c"]
/[[a-h]&&[f-z]]/.examples # => ["f", "g", "h"]