Readability is increased by explicitly checking if jquery/sendkeys was
already loaded before evaluating it in the context of ace_inner and the
enclosing container (pad.html). Note that sendkeys is no longer
evaluated in the context of ace_outer, as this isn't needed
Also removes some IE 8/9 legacy code
* Rename "current"/"other" to "user0"/"user1".
* Delete unnecessary `_createTokenFor*` functions.
* Rename helper functions to remove unnecessary leading underscore
and for brevity.
* Use jQuery's `.attr()` to build the second iframe.
* Use js-cookie to manipulate the token cookie.
* Don't attempt to set the token cookie if the pad isn't loaded.
* Use the token generated by the pad.
* Only clear the token cookie at path=/.
