3.1.0

Enhancements:

• yaml-set can now delete nodes when using --delete rather than other input
  arguments.
• A new command-line tool has been created, yaml-validate, which validates
  YAML/JSON/compatible single- and multi-documents (files or STDIN).

Bug Fixes:

• The yaml-merge command-line tool wasn't allowing Scalar values supplied via
  STDIN -- with no structure, just bare Scalar values -- to be appended to
  exising Array data structures; rather, it was wholly overwriting the
  destination, deleting all pre-exisiting elements.
• The yaml-merge command-line tool wasn't accepting empty-strings as STDIN
  documents; it was reporting a document-read error, instead. This turns out
  to be useful when you want to use yaml-merge instead of yaml-set to
  deliberately write an empty-string value at some --mergeat location within
  the LHS document.
• The yaml-merge command would not accept any variation of "false" as a Scalar
  value input; it was instead reporting a document-read error. This turns out
  to be useful when using yaml-merge as if it were yaml-set to write a false
  Boolean value to the LHS document at some --mergeat location.

API Changes:

• The func.get_yaml_data and func.get_yaml_multidoc_data functions now
  return/yield tuples. The first field is the desired yaml_data (can be None
  for empty documents) and the second field is a Boolean which indicates True
  when the document loaded with no errors or False when an error occurred.
  This is necessary in order to accept a bare "false" Scalar value as a
  STDIN-supplied document.