There are two ways to go about fixing this problem. As JustPucky mentioned, you can buy a resistor to add an extra load onto the circuit. The reason this helps is because the turn signal relay detects amount of draw on the circuit. With standard signal light bulbs, if one burns out, that side of your signal would blink faster to let you know you have a bulb burned out. Since the LED's don't draw near as much current, the relay senses that a bulb is out so it causes the light to blink faster. If you add a resistor, then the current is back to normal and the relay sees everything as working properly. However, the resistors get quite hot and could potentially start a fire. The risk is low, but it's still there. The other option to fix this problem is to replace your relay with a time delay relay, rather than the current sensing relay. Since you have LED bulbs all the way around, you don't have to worry about a bulb burning out so you don't really need the current sensing relay for the purpose which it was designed.
Hope that helps a bit.