Refresh build process and design

This is a significant reworking of the current site architecture.

The 3,080 additions and 267,653 deletions looks scary, but it is actually due to the switch to [grunt-gh-pages](https://github.com/tschaub/grunt-gh-pages). Compiled files (html, css, and js) will no longer be tracked on the `master` branch, but will instead be tracked only on the `gh-pages` branch.

## Technical Improvements

#### Cleaner documentation organization

* No more `core_docs.json` and `timezone_docs.json` files. Metadata is handled with yaml front matter in the markdown files.
* Added "edit" link on the documentation sections that links to the documentation source on GitHub. This should make contributing to the docs much easier.
* Instead of documentation being in `/source/core_docs/` and `/source/timezone_docs/`, they are now in `/docs/moment/` and `/docs/moment-timezone/`.
  In general, all references to `core` and `timezone` have been replaced with the more appropriately named `moment` and `moment-timezone`.

#### Easier local development

* Start server and watchers with `grunt server`.
* LiveReload changes to css, html, and js.
* File watchers for sass, js, or documentation changes.

#### Site html compilation with [assemble.io](http://assemble.io)

* No more hacked together html build process.
* All the benefits of assemble: layouts, helpers, partials, etc.
* Data for compiling site in `/data`, including list of languages and file sizes.
* Docs compiled from markdown to `.temp/docs/moment.json` via `grunt docs:moment`.

#### Deployments with [grunt-gh-pages](https://github.com/tschaub/grunt-gh-pages)

* `grunt deploy` will compile the site to `/deploy`, copy those files into the `gh-pages` branch, and push to GitHub.
* Generated html and assets are no longer tracked in the master branch of the repo.

#### Switched from Compass to libsass and autoprefixer

* Removes the Ruby dependency.

## Design improvements

#### Per project colors

* In order to differentiate between Moment and Moment Timezone, I gave each one its own color.
* The top level nav links also change colors to hint that those sections are relative to the current project.
* The specific colors for each section can be bikeshedded, but should have enough contrast for dark or light text.

#### Docs side nav

* Sections open and close while scrolling and highlight current section. Uses a modified version of jQuery.spyscroll.

#### Max widths

* I added a bunch of max-widths for content so that it doesn't stretch the full width of the browser.

## Screenshots

![Moment Home](https://cloud.githubusercontent.com/assets/643885/3281435/08795826-f4ad-11e3-8fda-a67e17e2c0e7.png)
![Moment Timezone Home](https://cloud.githubusercontent.com/assets/643885/3281438/087afff0-f4ad-11e3-8d91-b9c6002f5a4d.png)
![Moment Docs](https://cloud.githubusercontent.com/assets/643885/3281437/08798f9e-f4ad-11e3-89b6-95d16d711601.png)
![Moment Timezone Tests](https://cloud.githubusercontent.com/assets/643885/3281436/08795bfa-f4ad-11e3-96b7-aa95e7e2c039.png)