If you check out the tail end of that error, it gives you the line number that caused it - in this case, line 37 of the MotionApps20 file. If you check that out, you'll see:
#include "helper_3dmath.h"
Which means it's trying to include that particular header file. Based on the second error, you either don't have it at all or it's not in the right place. You can find it by going up a couple levels to https://github.com/jrowberg/i2cdevlib/tree/master/Arduino/MPU6050 and throwing everything there into the folder which you're working out of.
I had this thing working last summer, (building a quadrotor) but then school started up so I had to hang everything up until now. Back to square one!
