systools require registered attribute to be present in .app
Merge pull request #2 from yrashk/patch-1

systools require registered attribute to be present in .app
Fixing dependencies for erlpass.

No longer depend on PropEr, provide an alternative
rebar command & config for tests only.
Constant time check to avoid timing attacks

Timing attacks use the time it takes to return the result of hash
comparisons to figure out a good input for the password. This fix adds a
function that compares until it's done looking at the entire hash
instead of as soon as it finds a difference.

Fixes issue #3
Adding .app.src file

Generally useful for people with not-very-good cleanup scripts that just
delete the entirety of ebin/ directories.
use updated bcrypt with update rebar