Log Message:
Version 2.2.0 - March, 2017
---------------------------
- Bumped minor version number to reflect compatibility issues with
  OneOrMore and ZeroOrMore bugfixes in 2.1.10. (2.1.10 fixed a bug
  that was introduced in 2.1.4, but the fix could break code
  written against 2.1.4 - 2.1.9.)

- Updated setup.py to address recursive import problems now
  that pyparsing is part of 'packaging' (used by setuptools).

- Fixed KeyError issue reported by Yann Bizeul when using packrat
  parsing in the Graphite time series database, thanks Yann!

- Fixed incorrect usages of '\' in literals.

- Minor internal change when using '-' operator, to be compatible
  with ParserElement.streamline() method.

- Expanded infixNotation to accept a list or tuple of parse actions
  to attach to an operation.

- New unit test added for dill support for storing pyparsing parsers.
  Ordinary Python pickle can be used to pickle pyparsing parsers as
  long as they do not use any parse actions. The 'dill' module is an
  extension to pickle which *does* support pickling of attached
  parse actions.