Add more special characters

Related to this ticket
https://trello.com/c/fsuJOEDA/1678-club-shop-s-r-o-group-by-continuously-thinks

I added support for two more characters (\u001b and \u009b) and added some helpful comments for future explorers so that they may be saved from what I went through on this.

Resources:
http://php.net/manual/en/regexp.reference.unicode.php
http://www.codeproject.com/Articles/37735/Searching-Modifying-and-Encoding-Text

##### Functional test
Note:  I live edited this change on dash dev and it appeared to work for this issue
- Load this version and make sure nothing bad happens with normal charts in the category cache (the values populating the chart Group By dropdowns).
- Make sure there nothing else breaks with json encoding.