pywb update: update config for pywb 0.5.0
update wombat.js and set pywb==0.5.0 in reqs
use pywb develop branch for now to test latest fixes
check_dark_archive command and tests
increased size limit to 100MB
update to pywb 0.5.1
Merge pull request #598 from ikreymer/dev.pywb-0.5.0

Update pywb to 0.5.1
Add sauce testing.
Fix test.
Merge pull request #607 from jcushman/dev-dark_archive

Just merging this straight in, since it doesn't affect the server code, just tooling.