Add contributing section about pre-releases
Add contributing section about pre-releases

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