Update clj-http from 0.6.5 to 0.9.2

Update clj-http to a more recent version that contains fixes that are
useful in leiningen plugins.
Merge pull request #1596 from hugoduncan/feature/update-clj-http-to-0.9.2

Update clj-http from 0.6.5 to 0.9.2
Merge remote-tracking branch 'upstream/master'