Convert documentation front page back into markdown, remove reference to MetaSearch and reference Rails 4 supported by master.
Convert documentation front page back into markdown, remove reference to MetaSearch and reference Rails 4 supported by master.

varyonic/activeadmin,mrjman/activeadmin,waymondo/active_admin,varyonic/activeadmin,mauriciopasquier/active_admin,gogovan/activeadmin,activeadmin/activeadmin,javierjulio/activeadmin,maysam/activeadmin,deivid-rodriguez/activeadmin,SoftSwiss/active_admin,cmunozgar/activeadmin,wspurgin/activeadmin,wspurgin/activeadmin,mauriciopasquier/active_admin,vraravam/activeadmin,varyonic/activeadmin,vytenis-s/activeadmin,deivid-rodriguez/activeadmin,vraravam/activeadmin,gogovan/activeadmin,vraravam/activeadmin,mrjman/activeadmin,javierjulio/activeadmin,waymondo/active_admin,SoftSwiss/active_admin,gogovan/activeadmin,siutin/activeadmin,wspurgin/activeadmin,activeadmin/activeadmin,maysam/activeadmin,maysam/activeadmin,siutin/activeadmin,siutin/activeadmin,cmunozgar/activeadmin,activeadmin/activeadmin,SoftSwiss/active_admin,cmunozgar/activeadmin,vytenis-s/activeadmin,waymondo/active_admin,mauriciopasquier/active_admin,javierjulio/activeadmin,vytenis-s/activeadmin,mrjman/activeadmin,deivid-rodriguez/activeadmin