Integration with G+ added

Hi! First of all - thank you for nice plugin.

This is improvement for social comments added support for G+ comments.
Details about this (undocumented so far) feature here: http://browsingthenet.blogspot.ru/2013/04/google-plus-comments-on-any-website.html

Sample how it works you can see on our site: http://www.emdev.ru/-/video-liferay-portal-and-activiti-bpmn-integration

I hope you will find it useful and will able to place with new version into marketplace.