merge commit.
Merge branch 'master' of https://github.com/correlllab/cu-droplet
committing before pull
Merged DropletCustomTwo.cpp to match with HEAD.
Merge branch 'tile_assembly' of https://github.com/correlllab/cu-droplet into tile_assembly
Added function get_32bit_time in droplet sim.
Merge branch 'tile_assembly' of https://github.com/correlllab/cu-droplet into tile_assembly