insert messageEvolve into correct locations, replacing incorrect messageAlreadyMount

Currently, when you feed a pet enough to turn it into a mount, you see the messageAlreadyMount notification ("You already have that mount. Try feeding another pet."). This fix changes it to the messageEvolve notification ("You have tamed <%= egg %>, let's go for a ride!").
Merge pull request #217 from Alys/messageEvolve

insert messageEvolve into correct locations, replacing incorrect messageAlreadyMount