Update jsonld dependency.

Was broken on Node 4.x.

Author: RubenVerborgh

package.json

@@ -20,7 +20,7 @@
   "dependencies": {
     "qejs": "^3.0.0",
     "n3": "^0.4.0",
-    "jsonld": "^0.3.0",
+    "jsonld": "^0.4.2",
     "request": "^2.27.0",
     "mime": "^1.2.11",
     "negotiate": "^1.0.1",