fixes for wordpress 3.9 - specifically the editor button and popup

git-svn-id: https://plugins.svn.wordpress.org/activecampaign-subscription-forms/trunk@894309 b8457f37-d9ea-0310-8a92-e5e31aec5664
added new JS file and updated readme version tested

git-svn-id: https://plugins.svn.wordpress.org/activecampaign-subscription-forms/trunk@894310 b8457f37-d9ea-0310-8a92-e5e31aec5664