Refactor the sharing button

Move the button to a separate file
Create 2 new button styles (Icon and Icon+text)
Make sure it's compatible with Jetpack 3.0
Update readme.txt


git-svn-id: https://plugins.svn.wordpress.org/vk-sharing-jetpack/trunk@923898 b8457f37-d9ea-0310-8a92-e5e31aec5664