Fixed Twitter OAuth, added options

Changes made by Team Mandiberg

* Added option to keep or remove hashtagged words in retrieved posts.
* Added functionality to store more metadata from posts retrieved from
Twitter and Instagram, including:
  * URL to post on Twitter/Instagram
  * URL to user on Twitter/Instagram
  * Timestamp for post from Twitter/Instagram
* Exposed metadata from retrieved posts to be displayed in the archive
page.
* Added option to keep or remove Emoji from retrieved posts.
* Added option to whitelist usernames.
* Added option to pick a wordpress user to use as the author for
social-hashtag posts.