Extend the new canonicalizer to Draft 7 (#711)

Signed-off-by: Juan Cruz Viotti <jv@jviotti.com>

Author: jviotti

schemas/Makefile

@@ -1,5 +1,5 @@
-SCHEMAS = canonical-draft4.json canonical-draft6.json
-TESTS = canonical-draft4.test.json canonical-draft6.test.json
+SCHEMAS = canonical-draft4.json canonical-draft6.json canonical-draft7.json
+TESTS = canonical-draft4.test.json canonical-draft6.test.json canonical-draft7.test.json
 JSONSCHEMA ?= jsonschema
 
 .PHONY: all