bumping to 2.0.1
Merge branch 'master' of github.com:tenderlove/psych

* 'master' of github.com:tenderlove/psych:
  [#163] Add license to gemspec, is MIT
  * ext/psych/yaml/yaml.h: [DOC] fix typo by @GreenGeorge [Fixes GH-161]   https://github.com/tenderlove/psych/pull/161