Fixing link in README.
Adding support for custom characters.

This will probably never be merged into master due to the difficulty of
parsing and escaping the string so that it exactly matches what was
entered.
Changing custom text method.

Custom text is now parsed for a set of bad characters, which are then
removed before adding the element.
Now only checking for evil chars when add button is pressed.
Merge branch 'master' into gh-pages