Fixed issue defaulting year and month when not provided

 - In some circumstances the method would receive either an empty
   string or false rather than an undefined argument. This wasn't being
   checked for
Target _blank rather than _target for new window
Fixed the demo page so it would load

 - There are still some minor issues, and I'd like to remove the
   dependency on PHP (unless specifically requested for) so by default
   the other calendars will load correctly.