Merge pull request #14 from gboone/master

Creates fieldset functionality
Fixes meta box fieldsets

- Fieldsets no longer save as keys to arrays, they save as strings to unique
  meta_keys
Merge branch 'master' of github.com:cfpb/cms-toolkit
Merge branch 'master' of github.com:gboone/cms-toolkit into fieldset-fix
Merge branch 'fieldset-fix' of github.com:gboone/cms-toolkit into fieldset-fix
Touches up test documentation for 1.2 release
Updated documentation for fieldsets to reflect changes in #15