Add Upgrade section to Readme
Add Upgrade section to Readme

This commit adds an upgrade section to the README file.
Jandersolutions/font-awesome-sass,gnagel/font-awesome-sass,chepri/font-awesome-sass,Swrve/font-awesome-sass,Jandersoft/font-awesome-sass,rmwbweb/font-awesome-sass,sytzeloor/font-awesome-sass,FortAwesome/font-awesome-sass,mromulus/font-awesome-sass