Upgrade clojure to 1.5.1

This requires a bump in the version of swank, to get 1.5.x
compatibility.
Upgrade to latest cheshire
Update libs
Upgrade nrepl
Upgrade tools.namespace
Upgrade cheshire
Upgrade tools.cli and clj-stacktrace
Clojure 1.5 obsoletes our use of core.incubator
Upgrade clj-time
Upgrade jmx
Upgrade ring
Upgrade at-at, ring-mock, postgresql, log4j
Remove vestigial memoization of digest/sha-1

The new version of the digest library has switched from using a
multimethod (which is slower) to a protocol (which is faster).
Merge pull request #583 from grimradical/update-libs

Library and dependency refresh