Revert "* Fixed a debug error complaining about `extended_valid_elements`"

This reverts commit 2dc19b355a23e73872c44ef36a5773ed9d53448c.
* Fixed a debug error complaining about `extended_valid_elements`
undefined in `add_valid_tiny_mce_elements`
Merge pull request #4 from morganestes/extended_valid_elements

Fixed a debug error complaining about `extended_valid_elements` undefined in `add_valid_tiny_mce_elements`
Add support for new oEmbed URL format.

oEmbed is now the preferred embed type for WordPress.
Update readme.
Check if extended_valid_elements is a string before concatenating to it.
Merge branch 'master' of git://github.com/wistia/wistia-wordpress-plugin

# By Max Schnur (3) and Morgan Estes (1)
# Via Max Schnur
* 'master' of git://github.com/wistia/wistia-wordpress-plugin:
  Check if extended_valid_elements is a string before concatenating to it.
  Update readme.
  Add support for new oEmbed URL format.
  * Fixed a debug error complaining about `extended_valid_elements` undefined in `add_valid_tiny_mce_elements`