Merge pull request #564 from metabase/remove_data_json_dep

remove unused clojure.core/data.json dep

project.clj

@@ -11,7 +11,6 @@
                  [org.clojure/math.numeric-tower "0.0.4"]             ; math functions like `ceil`
                  [org.clojure/core.memoize "0.5.7"]                   ; needed by core.match; has useful FIFO, LRU, etc. caching mechanisms
                  [org.clojure/data.csv "0.1.2"]                       ; CSV parsing / generation
-                 [org.clojure/data.json "0.2.6"]                      ; JSON parsing / generation
                  [org.clojure/java.classpath "0.2.2"]
                  [org.clojure/java.jdbc "0.3.7"]                      ; basic jdbc access from clojure
                  [org.clojure/tools.logging "0.3.1"]                  ; logging framework