merging develop
Cleaning up library to not use this._a[8] hacks. Parser/constructor now uses a config object that stays throughout the input process for methods to attach any data to the final moment object
Failing tests for #455
Passing tests for #455
Bumping version number for #455
Merge branch 'hotfix/1.7.2'

* hotfix/1.7.2:
  Bumping version number for #455
  Passing tests for #455
  Failing tests for #455
Updating readme with changelogs
Merging in develop
merging in feature/constructor-refactor
Language cleanup
Fixing race condition that is causing failing TravisCI tests
Adding tests and fix for #462 on develop
Merge pull request #460 from timrwood/feature/lang-cleanup

Language cleanup
Adding moment.fn.toJSON

#444
Updating preparse and postformat from #405 to use new parsing + language internals
Failing tests for #470
Passing tests for #470
Failing unit tests for singular add/subtract #410
Passing unit tests for singular add/subtract #410
Failing tests for adding singular/plural getters and setters #410