Replace html entities with < > & " ' in imgur/tumblr expandos

imgur and tumblr post expandos have been showing HTML entities in the titles and captions since [`innerHTML` was phased out in favor of `textContent`](https://github.com/honestbleeps/Reddit-Enhancement-Suite/commit/7f8949f6b36e2f075890cdc0f5854d439e48ab2f). This change replaces the most common HTML entities with their text equivalents: `< > & " '`

[relevant post](http://www.reddit.com/r/RESissues/comments/13pad3/bug_ampersands_in_imgur_album_picture_titles_are/)