AddGTest should reference Lookup-GTest
AddGTest should reference Lookup-GTest

GTest -> LookupGTest happened in 82b7b247.
Closes #44

UCL/GreatCMakeCookOff,UCL/GreatCMakeCookOff,UCL/GreatCMakeCookOff,UCL/GreatCMakeCookOff