"Port" the front-end scripts to TypeScript

[eddieantonio]

@mdfeist I need your blessing to do this, since this involves a change in workflow. The new workflow involves having the TypeScript compiler in watch mode (tsc --watch) while editing the files. And of course, you may add optional type annotations to functions. Editing TypeScript within Atom (and maybe Sublime?) enables watch mode by default, and provides all of the fun static analysis.

The porting process:

• [x] Create tsconfig.json
• [x] Change all sources to .ts extension

The advantages:

• [x] Get rid of all type asserts
• [x] Create one destination file
• [x] Actually working source maps (our current workflow creates source maps that are off by one line?)
• [x] Compile to ES5 (since we're currently using ES6 features that may not be universally supported)
• [x] Editor autocompletion
• [x] Safer refactoring

Optional:

• [x] Create a definition file for the JSON generated by the Flask web service

[eddieantonio]

I've done work on this in the typescript branch. Since I've fixed a few bugs in this branch, I'd like to merge it, but I have a few TODOs:

• [x] Document how to get tsc, typings, and maybe even Node 4.0.
• [x] Document how to use typings install and tsc properly
• [x] Document how I develop (use Atom-Typescript, save files, press F6 when I'm paranoid).