minor change to compile and run on GPU
fixed host v.s. device vector problem, now haloMergeTreeGPU is working
Merge branch 'master' of github.com:wathsy/PISTON into halo
change halo.cu a sym link of halo.cpp, remove bogus compiler flag, disable console output in device code
resolve conflicts in wathsy's branch
included avg positions & velicities to the merge tree & other minor changes
resolving conflicts