Add Tomcat version support docs to README.
Add Tomcat version support docs to README.

xloye/tomcat-redis-session-manager,changming8/tomcat-redis-session-manager,zhoffice/tomcat-redis-session-manager,sunqb/tomcat-redis-session-manager,jcoleman/tomcat-redis-session-manager,fengshao0907/tomcat-redis-session-manager,treejames/tomcat-redis-session-manager,bpzhang/tomcat-redis-session-manager,bsr1983/tomcat-redis-session-manager,fengshao0907/tomcat-redis-session-manager,shaunwkelly/tomcat-redis-session-manager,xloye/tomcat-redis-session-manager,accountwcx/tomcat-redis-session-manager,jcoleman/tomcat-redis-session-manager,zhoffice/tomcat-redis-session-manager,rmohr/tomcat-redis-session-manager,AustinKwang/tomcat-redis-session-manager,mlc0202/tomcat-redis-session-manager,changming8/tomcat-redis-session-manager,michaelcameron/tomcat-redis-session-manager,alex-bretet/tomcat-redis-session-manager,crazyABC/tomcat-redis-session-manager,mlc0202/tomcat-redis-session-manager,accountwcx/tomcat-redis-session-manager,liuxinglanyue/tomcat-redis-session-manager,280455936/tomcat-redis-session-manager,crazyABC/tomcat-redis-session-manager,janrain/tomcat-redis-session-manager,AustinKwang/tomcat-redis-session-manager,alex-bretet/tomcat-redis-session-manager,sunqb/tomcat-redis-session-manager,rmohr/tomcat-redis-session-manager,treejames/tomcat-redis-session-manager,deeplyloving/tomcat-redis-session-manager,icoding/tomcat-redis-session-manager,gspandy/tomcat-redis-session-manager,icoding/tomcat-redis-session-manager,ardorleo/tomcat-redis-session-manager,hanyahui88/tomcat-redis-session-manager,deeplyloving/tomcat-redis-session-manager,myliferepo/tomcat-redis-session-manager,gspandy/tomcat-redis-session-manager,michaelcameron/tomcat-redis-session-manager,280455936/tomcat-redis-session-manager,bpzhang/tomcat-redis-session-manager,liuxinglanyue/tomcat-redis-session-manager,ardorleo/tomcat-redis-session-manager