Update to preact 4 for tests

Author: developit

package.json

@@ -35,7 +35,7 @@
     "chai": "^3.3.0",
     "eslint": "^1.7.1",
     "mocha": "^2.3.3",
-    "preact": "^3.3.0",
+    "preact": "^4.1.3",
     "sinon": "^1.17.1",
     "sinon-chai": "^2.8.0"
   }