Bump codox dependency tp 0.6.4
Bump Clojure version in 1.5 profile up to 1.5.0
Bugfix: Not-modified-since condition corrected.

Date comparison condition is inverted.
In particular equal dates produce 304 response.
Updated tests.
Conservative fix for header names comparison.
Merge pull request #49 from PetrGlad/50b3611027b686f88c41cd0d34ddaca363b65917

Corrected date comparison between If-Modified-Since and Last-Modified header values.
Merge pull request #51 from kavu/upate_clojure_version

Bump Clojure version in 1.5 profile up to 1.5.0
Merge pull request #52 from kavu/update_codox_dependency

Bump codox dependency to 0.6.4
Add ring.util.response/get-header utility
Unify response header handling to use get-header, fixes #50
Bump to clojure version 1.5.1 in 1.5 profile