Fix Event Calendar Caching

The “All-in-One Event Calendar” by Time.ly works great, but uses dynamic javascript.
This plugin creates a static version of the javascript that can be cached by
the browser.

I have tested this plugin with versions 2.1.9 and 2.2.0 of the event calendar plugin.
It may work with future releases, but use it at your own risk.

This plugin only uses the static javascript on the frontend. If a user is
logged in, the original dynamic script will be used. As far as I can tell
caching the javascript does not interfere with the plugin’s functionality, but
there may be features of the event calendar that do not work with this plugin.