update plugin guide with module loader info

PLUGIN-GUIDE.md

@@ -15,6 +15,13 @@ This guide lists a number of best practices for publishing a Leaflet plugin that
 	- [File Structure](#file-structure)
 	- [Code Conventions](#code-conventions)
 	- [Plugin API](#plugin-api)
+3. [Module Loaders](#module-loaders)
+	- [Wrapping with UMD](#wrapping-with-umd)
+	- [Using with RequireJS](#using-with-requirejs)
+	- [Using with Browserify](#using-with-browserify)
+	- [Best practices for RequireJS](#best-practices-for-requirejs)
+	- [Best practices for Browserify](#best-practices-for-browserify)
+	- [Module Loader Resources](#module-loader-resources)
 
 ## Presentation
 
@@ -125,3 +132,115 @@ marker.myPlugin('bla', {
 ```
 
 And most importantly, keep it simple. Leaflet is all about *simplicity*.
+
+## Module Loaders
+
+Module loaders such as [RequireJS](http://requirejs.org/) and [Browserify](http://browserify.org/) impliment module systems like AMD (Asyncronous Module Definition) and CommonJS to allow developers to modularize and load their code.
+
+Leaflet supports being loaded as either an AMD module or a CommonJS module. It does this by implimenting UMD (Universal Module Definition) which checks for the existance of an AMD/CommonJS and impliments the appropriate wrappers.
+
+### Wrapping with UMD
+
+You can add support for AMD/CommonJS loaders to your Leaflet plugin by follwoing this pattern.
+
+```js
+(function (factory, window) {
+
+    // define an AMD module that relies on 'leaflet'
+    if (typeof define === 'function' && define.amd) {
+        define(['leaflet'], function (L) {
+            return (exports = factory(L));
+        });
+    
+    // define a Common JS module that relies on 'leaflet'
+    } else if (typeof exports === 'object') {
+        module.exports = factory(require('leaflet'));
+    
+    }
+
+    // attach your plugin to the global 'L' variable
+    window.L.YourPlugin = factory(L);
+
+}(function (L) {
+    // impliment your plguin
+    var MyLeafletPlugin = {};
+
+    MyLeafeltPlugin.CustomLayer = L.Layer.extend({
+        onAdd: function(map){
+
+        },
+        onRemove: function(){
+
+        }
+    });
+
+    // return your plugin when you are done
+    return MyLeafletPlugin;
+}, window));
+```
+
+### Using with RequireJS
+
+Now users using RequireJS (which impliments the AMD module system) can use your plugin like this.
+
+```js
+// define where the 'leaflet' and 'your-plugin' modules are located
+require.config({
+    paths: {
+        'leaflet': 'the/path/to/leaflet', //path to leaflet.js without the .js
+        'your-plugin': 'the/path/to/your-plugin', //path to your-plguin.js without the .js
+    }
+});
+
+require([
+    'leaflet',
+    'your-plugin'
+], function(L, YourPlugin) {
+    var map = new L.map('map').setView([45.5, -122.75], 9);
+    var layer = new YourPlugin.CustomLayer().addTo(map);
+});
+```
+
+### Using with Browserify
+
+Users who are using Browserify (which impliments the CommonJS module system) can use your plugins following this example.
+
+```js
+var L = require('leaflet');
+var YourPlugin = require('your-plugin');
+
+var map = new L.map('map').setView([45.5, -122.75], 9);
+var layer = new YourPlugin.CustomLayer().addTo(map);
+```
+
+### Best practices for RequireJS
+
+Most AMD based module systesm (RequireJS, Dojo, ect...) have a mechanisum to name modules so they can be easily included with short strings rather then paths. In order to avoid confusion with many short names like `Leaflet` vs `leaflet` always use a lowercase `leaflet` for your module identifier.
+
+### Best practices for Browserify
+
+CommonJS module systems like Browserify rely on the [NPM (Node Package Modules)](https://www.npmjs.org/) registry to manage their dependencies. The means that when you `require('leaflet')` the proper module from the registry is returned to you.
+
+This means that you must publish your plugin to the NPM repository. NPM has an excellent [developers guide](https://www.npmjs.org/doc/misc/npm-developers.html) to help you through the process.
+
+When you publish your plugin you should add a depenency on `leaflet` to your `package.json` file. This will automatically install Leaflet when your package is installed.
+
+```json
+{
+  "name": "my-leaflet-plugin",
+  "version": "1.0.0",
+  "description": "A simple leaflet plugin.",
+  "main": "my-plugin.js",
+  "author": "You",
+  "license": "IST",
+  "dependencies": {
+    "leaflet": "^1.0.0"
+  }
+}
+```
+
+### Resources
+
+* [Get started with RequireJS](http://requirejs.org/docs/start.html#add)
+* [Get started Browserify](https://github.com/substack/browserify-handbook)
+* [Publishing on NPM](https://www.npmjs.org/doc/misc/npm-developers.html)