Refactor namespaces to modules

[ejizba]

Tangentially related to #12, a lot of places (example here and here) say not to use namespaces for organizational reasons. Instead, they say use modules and re-export where necessary. In other words, instead of something like this:

export namespace app { ... }

Just put the code in a separate file and re-export it like this:

export * as app from './app';

At least, that's my interpretation. Functionally, this makes very little difference to our package (no changes necessary to the prototype). The PR is mostly just splitting code into separate files.

[ejizba]

Fwiw, I did split this up into separate commits to make it easier to review. The first commit just moves the code. The second commit is what actually converted to namespaces and is the interesting piece to review. It should also be viewed with whitespace changes off: 920bbab?w=1

[hossam-nasr]

LGTM! I also like that this reduces the length of our index.ts and index.d.ts and nicely separates code :)