docs - remove references to web3-provider-engine

docs/developing-on-deps.md

@@ -1,10 +1,9 @@
 ### Developing on Dependencies
 
-To enjoy the live-reloading that `gulp dev` offers while working on the `web3-provider-engine` or other dependencies:
+To enjoy the live-reloading that `gulp dev` offers while working on the dependencies:
 
  1. Clone the dependency locally.
  2. `npm install` in its folder.
  3. Run `npm link` in its folder.
  4. Run `npm link $DEP_NAME` in this project folder.
  5. Next time you `npm start` it will watch the dependency for changes as well!
-

docs/porting_to_new_environment.md

@@ -79,8 +79,6 @@ MetaMask has two kinds of [duplex stream APIs](https://github.com/substack/strea
 
 If you are making a MetaMask-powered browser for a new platform, one of the trickiest tasks will be injecting the Web3 API into websites that are visited. On WebExtensions, we actually have to pipe data through a total of three JS contexts just to let sites talk to our background process (site -> contentscript -> background).
 
-To make this as easy as possible, we use one of our favorite internal tools, [web3-provider-engine](https://www.npmjs.com/package/web3-provider-engine) to construct a custom web3 provider object whose source of truth is a stream that we connect to remotely.
-
 To see how we do that, you can refer to the [inpage script](https://github.com/MetaMask/metamask-extension/blob/master/app/scripts/inpage.js) that we inject into every website. There you can see it creates a multiplex stream to the background, and uses it to initialize what we call the [inpage-provider](https://github.com/MetaMask/metamask-extension/blob/master/app/scripts/lib/inpage-provider.js), which you can see stubs a few methods out, but mostly just passes calls to `sendAsync` through the stream it's passed! That's really all the magic that's needed to create a web3-like API in a remote context, once you have a stream to MetaMask available.
 
 In `inpage.js` you can see we create a `PortStream`, that's just a class we use to wrap WebExtension ports as streams, so we can reuse our favorite stream abstraction over the more irregular API surface of the WebExtension. In a new platform, you will probably need to construct this stream differently. The key is that you need to construct a stream that talks from the site context to the background. Once you have that set up, it works like magic!