Roots 7.0.0

* [x] Add Bower (#922, #978)
* [x] Better LESS organization (#961)
* [x] Different Grunt workflow (#933)
* [x] Leaner Roots (#992) — clean up, relative URLs, and nice search moved to [Soil](https://github.com/root/soil)
* [x] Update screenshot to 880x660 (maybe just use a blank image)
* [ ] Merge in @Foxaii's [nav rejig](https://github.com/roots/roots/commits/nav_rejig)
* [x] [Move language files outside repo](https://github.com/roots/roots-translations)
* [x] Add grunt-autoprefixer
* [ ] Setup `dist/` folder?
* [x] Generate new `roots.pot`
* [x] Update CHANGELOG
* [x] Update README
* [x] Update roots.io docs



## What's new

### Leaner Roots

[Soil](https://github.com/roots/soil) will now be a plugin that contains:

* Markup changes/clean up
  * `wp_head()` clean up
  * Remove WP version from RSS feeds
  * Clean up `<html>` attributes
  * Clean up `<link>` tags
  * Clean up `body_class()`
  * Wrap embedded media as suggested by Readability
  * Use `<figure>` and `<figcaption>` for WP captions
  * Remove unnecessary dashboard widgets
  * Remove unnecessary self-closing tags
* Nice search
* Relative URLs

The above features will be enabled in Roots (or any other theme) if Soil is activated by using `add_theme_support`:

* `add_theme_support('soil-clean-up');`
* `add_theme_support('soil-nice-search');` 
* `add_theme_support('soil-root-relative-urls');` 

Removed from Roots:

* `lib/cleanup.php` - Move `roots_get_search_form` to `lib/utils.php`
* `lib/widgets.php` - Remove vCard widget, move register sidebars to `lib/init.php`
* `lib/relative-urls.php`

### Bower for front-end package management
[Bower](http://bower.io/) is now being used to pull in Modernizr, jQuery, Bootstrap and Respond to `assets/vendor/`. Whenever you're adding front-end assets to your project, you can use `bower install <package>` to add them to the vendor directory.

We're also now using [grunt-modernizr](https://github.com/Modernizr/grunt-modernizr) to make a lean build based on what tests you use in your styles and JS.

If you check out the `7.0.0` branch, run `npm install` from the theme dir and `bower install` will run after the node dependencies have been installed.

### LESS organization

LESS files are organized differently, see #961 for details. tl;dr:

```
├── components
│   ├── _buttons.less
│   ├── _forms.less
│   ├── _media.less
│   └── _wp-classes.less
├── layouts
│   │── pages
│   │   └── _home.less
│   │── _footer.less
│   │── _general.less
│   │── _header.less
│   │── _pages.less
│   │── _posts.less
│   └── _sidebar.less
├── _bootstrap.less
├── _global.less
├── _variables.less
└── main.less
```

### Grunt workflow

Previously, every time you updated your CSS or JS, a minified files and changes to `lib/scripts.php` had to be committed to the repo. The repo no longer includes any generated front-end assets. Grunt tasks are now split into two: `dev` and `build`.

The `dev` task runs JSHint, compiles your LESS (non-minified) and concatenates your JS

The `build` task runs JSHint, compiles and minifies your LESS, runs UglifyJS for concatenation and minification, generates a lean Modernizr build, and revisions CSS and JS based on the hashes.

During `build`, `assets-manifest.json` is generated with the names of the revisioned files. `lib/scripts.php` reads that file and tells WordPress the correct path to the assets.

## Testing

Check out the `7.0.0` branch and run `npm install` from the theme directory. If you don't use [Bedrock](https://github.com/roots/bedrock), you'll need to add the following to your `wp-config.php`:

```php
define('WP_ENV', 'development');
```

Grunt tasks:

* `grunt dev`
* `grunt watch` (same as `dev` except watches for file changes)
* `grunt build` — for staging/production

Also grab [https://github.com/roots/soil](Soil)'s `new` branch and enable the plugin

## Note: things are subject to change!

These changes are not yet final. Keep an eye on this PR for updates.