So I did a bit of digging and found this: I guess when you want to evolve an Eevee, you are going to get a random one every time. Sometimes you may end up with nothing but the same one so if you want all three, be sure to catch a lot of Eevees! This is somewhat simple I guess because they are common though I have yet to find one myself. I have only been playing for two days though!
They've found a way to evolve Eevee to the desired eeveelution, check this guide Just name your Eevee Sparky for Jolteon, Pyro for Flareon or Rainer for Vaporeon. Note that Vaporeon is the strongest pokemon in game: http://pkmngotrading.com/wiki/Why_Vaporeon_Is_Overpowered
YUP! I heard the same thing and I know someone who did it and it worked. I guess this was a cheat meant for only some people to know about. I expect an update to change this in the future.
I thought the Eeveelution you got depended on a move it has too, maybe I'm wrong. Is the name thing confirmed?
It is confirmed but only works the one time. So after you have a jolteon, vaporeon, and flareon, then the Eevee evolutions are completely random. The move was a theory but I don't think was ever confirmed. I still think it is random.
I was able to get Vaporeon and Flareon doing this but Jolteon did not work. I am starting to think it was only by chance not by the name that I got them.