Add web3-provider-engine devDep for tests

Author: dmihal

package.json

@@ -72,6 +72,7 @@
     "ts-node": "^8.3.0",
     "tslint": "^5.12.0",
     "typescript": "^3.2.2",
-    "typestrict": "^1.0.2"
+    "typestrict": "^1.0.2",
+    "web3-provider-engine": "^15.0.7"
   }
 }