Update MongoDB versions tested in travis
Update MongoDB versions tested in travis

rinmu/mongoid,mongodb/mongoid,nviennot/mongoid,kay-kim/mongoid,estolfo/mongoid,kay-kim/mongoid,Sharevari-Inc/mongoid,estolfo/mongoid,uniiverse/mongoid,nviennot/mongoid,tzar/mongoid,rinmu/mongoid,jbrien/mongoid,Sharevari-Inc/mongoid,herimedia/mongoid,drobune/mongoid,herimedia/mongoid,jbrien/mongoid,uniiverse/mongoid,Zhomart/mongoid,drobune/mongoid,Welovroi/mongoid,Welovroi/mongoid,tzar/mongoid,Zhomart/mongoid,jonhyman/mongoid,jonhyman/mongoid,nicolasblanco/mongoid,mongodb/mongoid,mongodb/mongoid