On solaris flavors, `which` has: sometimes poor behavior of not returning proper exit codes or printing errors to STDOUT rather than STDERR. All of this is to say, the makefile didn't behave correctly on Solaris. $(REBAR) ended up being set to "rebar not found" which made the compile target less than happy. I added a print-* target to test this easier. Simply `make print-VAR` to see the value. So `make print-REBAR` will show you the value of $REBAR.
Add a makefile target following Kenji Rikitake's procket-chmod.sh script. Also, explain in the README how to call the setuid bin.
Remove local copy of the rebar script. Preferentially use the user's rebar script, if it exists in their path; otherwise, try to download it. Since the download is in the clear, a future improvement would check a hash before running the script.