Merge pull request #1 from tmjbradley/master

Remove deprecated cudaThreadSynchronize()
Update exercise.cu
Add first stab at introduction for README for the quad tree exercise.
Merge pull request #2 from tmjbradley/master

Added more_points exercise
Move the definition of bbox to util.h
Encapsulate point->tag transformation into point_to_tag function.
Narrate up to the first reduction
Narrate up to the sort
Add the parallel part of the "Linearizing the Points" section
Some small edits
Merge branch 'master' into gtc2013
Pull in latest edits to more_points