fix(0x.js): make web3-provider-engine types a 'dependency' so it's available to users of the library

packages/0x.js/package.json

@@ -53,7 +53,6 @@
         "@types/mocha": "^2.2.42",
         "@types/node": "*",
         "@types/sinon": "^2.2.2",
-        "@types/web3-provider-engine": "^14.0.0",
         "awesome-typescript-loader": "^5.2.1",
         "chai": "^4.0.1",
         "chai-as-promised": "^7.1.0",
@@ -85,6 +84,7 @@
         "@0xproject/typescript-typings": "^3.0.2",
         "@0xproject/utils": "^2.0.2",
         "@0xproject/web3-wrapper": "^3.0.3",
+        "@types/web3-provider-engine": "^14.0.0",
         "ethereum-types": "^1.0.11",
         "ethers": "~4.0.4",
         "lodash": "^4.17.5",