add supported-operating-systems tag to intro doc
add supported-operating-systems tag to intro doc

mbrukman/flocker,AndyHuu/flocker,adamtheturtle/flocker,mbrukman/flocker,w4ngyi/flocker,moypray/flocker,adamtheturtle/flocker,mbrukman/flocker,achanda/flocker,agonzalezro/flocker,agonzalezro/flocker,adamtheturtle/flocker,1d4Nf6/flocker,wallnerryan/flocker-profiles,1d4Nf6/flocker,Azulinho/flocker,hackday-profilers/flocker,AndyHuu/flocker,hackday-profilers/flocker,1d4Nf6/flocker,agonzalezro/flocker,Azulinho/flocker,moypray/flocker,w4ngyi/flocker,Azulinho/flocker,hackday-profilers/flocker,wallnerryan/flocker-profiles,AndyHuu/flocker,achanda/flocker,wallnerryan/flocker-profiles,achanda/flocker,w4ngyi/flocker,moypray/flocker