2.0.0

Enhancements:

• Added Collectors to YAML Path expressions. These take the form of "(YAML
  Path)" -- parenthesis () are used to demarcate each Collector -- resulting in
  a list of zero or more matches for the sub-query. Operators between
  Collectors include + and -, like "(...)+(...)", "(...)-(...)", and nested
  Collectors are possible, like "(...)-((...)+(...))". Collectors may appear
  anywhere within the outer YAML Path, effectively setting the point within the
  data at which each Collector is rooted.
• A major code refactoring was undertaken to break YAMLPath out as its own class
  and improve code quality (per mypy and pylint).

Bug Fixes:

• yaml-set v1.0.4 now implies --mustexist when --saveto is set. Otherwise,
  --saveto was trying to save nothing when --change (without --mustexist)
  pointed nowhere.