Fixed Typos regarding OAuth tutorial.
Rewording the `Client_Credential` area to clarify that you're still passing `password` in the JSON.  Fixed Typos regarding OAuth tutorial.
Small typo.
[#23] Reviewed and edited

- Reverted the removal of the "Application access" section, as the changes made were incorrect.
- Added level 3 headers to differentiate the confidential/public use cases of the password grant
  type.
Merge branch 'hotfix/23'

Close #23