As mentioned by @guestguy123 and @eficker, it is easy to combine an EV3 cable and a PF cable to make a custom cable that allows the EV3 to control. This can even be done without soldering - I just twist the wires together and tape them with electrical tape. The full schematic is here:
All you need is 2 resistors (1x1kOhm and 1x10kOhm) which are cheap to get at your local electronics store (e.g. Radioshack or Maplin's) and the willpower to cut through 2 good Lego wires (1 PF cable and 1 EV3 cable). But once you do, it recognizes a PF motor as an NXT style unregulated motor and you can send it commands.