a standalone example that doesn't require Node.js

[tylerxue]

a standalone example that doesn't require Node.js, RequireJs and Browserify and other unnecessary external dependencies.

[jlin27]

Thanks for the PR @tylerxue.

Is this PR proposing changes that update the existing code to be an example that doesn't require Node.js, RequireJs, and Browserify or are you just suggesting that we create such an example?

If it is the second, have you checked out our Next.js Demo App. We have more examples in the 0x-examples repo.

If it is the first, can you please provide details on what code changes were made in this PR?

[tylerxue]

it's the first case, all changes are in the new folder named 'swap-demo-tutorial-part-tyler' which i think should be renamed if you plan to merge it.

1. remove qs.stringify by providing a substitute function 'build_query_string'.
2. include web3 and bignumber directly in the index.html:

so now for the app to start up and running, you dont need to install Node.js and build node_modules anymore. for a new learner, less dependencies, less complexities.