Moto E Not Starting Properly After Changing runtime to ART

I have recently bought a *MOTO E* and it's working cool. Then I have enabled *Developer options* and changed my runtime from *Dalvik* to *ART.* Afterwards I restarted my device. I got the message saying *Android is upgraging.* After completeing the process I got exceptions like unfortunately the process com.android.phone has stopped Please help me how to get out of this problem. I am getting that message for around 10 times and mobile restarting once again.