Version 2.2.0

- Added lexers:
  * AMPL
  * TypoScript
  * Varnish config
  * Clean
  * WDiff
  * Flatline
  * Silver
  * HSAIL
  * JSGF
  * NCAR command language
  * Extempore
  * Cap'n Proto
  * Whiley
  * Monte
  * Crystal
  * Snowball
  * CapDL
  * NuSMV
  * SAS, Stata
- Added the ability to load lexer and formatter classes directly from files
  with the `-x` command line option and the `lexers.load_lexer_from_file()`
  and `formatters.load_formatter_from_file()` functions.
- Added `lexers.find_lexer_class_by_name()`.
- Added new token types and lexing for magic methods and variables in Python
  and PHP.
- Added a new token type for string affixes and lexing for them in Python, C++
  and Postgresql lexers.
- Added a new token type for heredoc (and similar) string delimiters and
  lexing for them in C++, Perl, PHP, Postgresql and Ruby lexers.
- Styles can now define colors with ANSI colors for use in the 256-color
  terminal formatter.
- Improved the CSS lexer.
- Added "Rainbow Dash" style.
- Delay loading `pkg_resources`, which takes a long while to import.

(adam)