Disable html character encoding

As rails use utf8, there's no need for tinymce to convert characters to.
This makes stored database content cleaner, and it's easier to search the content.
Also, these entities will not display correctly if one tried to strip tags and truncate the content, like so:
truncate(strip_tags(article.content), length: 145, :separator => " ").html_safe

see: http://www.tinymce.com/wiki.php/Configuration:entity_encoding
Merge pull request #523 from baversjo/master

Disable html character encoding