Add "browserify" support

Hello scribe maintainers! I've added another method of consuming the scribe editor: [browserify](http://browserify.org/)

Changes required:

 1. Change `lodash-modern` require calls to `lodash-amd`, because this is the way that npm will install the `lodash-amd` module by default. We can make bower emulate the npm behavior easily.
 1. Add the `main` and `dependencies` field to the `package.json` file so that browserify knows the JavaScript entry point and npm knows the dependencies to install.
 1. Add the `browserify.transform` field to the `package.json` so that browserify knows to "deamdify" the scribe code into CommonJS.
 1. Updated the `Plumbing.js` build file to match the npm install output.

So now users can consume scribe via browserify via CommonJS code like this:

``` js
var Scribe = require('scribe');

var scribe = new Scribe(document.querySelector('rte'));
scribe.setContent('<p>Hello, World!</p>');

scribe.on('content-changed', updateHtml);
function updateHtml() {
  document.querySelector('.rte-output').value = scribe.getHTML();
}

updateHtml();
```

<del>__Note:__ depends on https://github.com/lodash/lodash-amd/pull/2 (and subsequently a new `lodash-amd` version update) in order to work properly.</del>

Any shot of this being merged into master branch? Cheers!