bump botframework-streaming to 4.11.0

[stevengum]

And add .vscode to .gitignore.

Testing:

1. Followed React Native's Setting up the development environment via the Expo CLI Quickstart route.
2. yarn add botframework-directlinejs to RN project (downloaded 0.14.0)
3. yarn add @expo/webpack-config to RN project (has dependency on Webpack 4)
4. Create webpack.config.js, modify file to not use node polyfills
5. Run yarn web, observed that it failed to build due not resolving 'stream'
6. Used yarn link to link RN project with local clone of this PR's branch stgum/bf-s/4.11
7. Run yarn web again, success.

webpack.config.js

const createExpoWebpackConfigAsync = require('@expo/webpack-config');

// Expo CLI will await this method so you can optionally return a promise.
module.exports = async function(env, argv) {
  const config = await createExpoWebpackConfigAsync(env, argv);
  // If you want to add a new alias to the config.
  config.resolve.alias['moduleA'] = 'moduleB';

  // Maybe you want to turn off compression in dev mode.
  if (config.mode === 'development') {
    config.devServer.compress = false;
  }

  config.node = false;

  // Or prevent minimizing the bundle when you build.
  if (config.mode === 'production') {
    config.optimization.minimize = false;
  }

  // Finally return the new config for the CLI to use.
  return config;
};

[stevengum]

Successful build (#473) for 28bc778 via Travis

[corinagum]

LGTM