Fix digest already in progress errors

The best solution here seems to be a timeout to ensure that it’s
respected in the digest and doesn’t produce “digest is already in
progress” errors.  Referenced here:
http://stackoverflow.com/questions/22346990/why-is-using-ifscope-phase-s
cope-apply-an-anti-pattern
Merge pull request #80 from tannerlinsley/master

Fix digest already in progress errors