Refactor

[FuqingWang]

Some update:

1. Refactored code into components for easier module management.
2. switched the app root from index.js to App.js (Optional, but starting with App.js is more like a convention that the react community follows. index.js is more of an application entry point, while app.js is the root of our app tree, where our component hierarchy starts. Generally we don't mess up with the entry point but the app tree)
3. rename the folder from "Components" to "components". (Also a conventional thing, lower case first letter for component folders. But for actual components we use upper case first letter)

[mfleader]

Can you remove package-lock.json in addition to yarn.lock? I want to take them out of version control since we have package.lock.

[FuqingWang]

Just removed those package-lock.json and yarn.lock.