Update dependencies
Make this an :each fixture

test-ls and test-ls-prefix were, i think, running in a different order
for me than when they were originally, so test-ls was failing because it
was seeing the objects that test-ls-prefix was leaving behind in the
bucket -- making this an :each fixture simplifies things because the
containers can be assumed to be empty
Fix typo, I think

I'm not sure how this was ever working as written
Upgrade to clj-http 1.0.0

which brings in clj-http's new header-map functionality. We no longer
need to worry about keywordizing-keys, but we do need to use care when
merging the :headers map with other things in order to preserve the
header-map-ness of it.