main.cpp: set the default of draw joints to TRUE
gitignore: remove trailing slash on build
HACK: print out joint locations when drawing

On each frame print "FRAME" to standard out. When processing each user
print "USER:<n>" to standard out and then for each joint print:

    JOINT:<n>,<x>,<y>,<z>,<u>,<v>

where n is the user id, x, y and z are the 3D co-ordinates of the joint
and u, v are the 2D co-ordinates.