Fixed IC2 conversion ratio

I'm 99.9% sure the IC2 ratio wrong (it was inverted, relative to the BC ratio). This should be the right one. At least this way one coal gives me the same amount of energy from a BC Stirling Engine and an IC2 Generator (minus the 0.01% loss in BC).
Fixed ratio computation, was always zero due to integer division
Merge pull request #167 from fnuecke/patch-1

Fixed IC2 conversion ratio and ratio computation