Extract libraries to an separate extension.

assets/leaflet-ajax/README.md

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+leaflet-ajax
+===========
+
+Allows you to call JSON via an Ajax call with a jsonp fallback.
+
+```javascript
+var geojsonLayer = new L.GeoJSON.AJAX("geojson.json");
+```
+for jsonp add the option "dataType" and set it to "jsonp"
+``` javascript
+var geojsonLayer = L.geoJson.ajax("http:webhost.fake/geojson.jsonp",{dataType:"jsonp"});
+```
+Note that data starts to download when the layer is created NOT when it’s added to the map in order to get a head start.
+
+You may pass either a url string or an array of url strings if you want to download multiple things (handy
+if your downloading data from an ESRI based thing which will have separate line, point, and poly features).
+
+As you see you can also use lower case methods without creating new objects
+
+For weirder jsonp you can set "callbackParam" for if you need to change the name of the callback parameter to something besides "callback", e.g. [Mapquest Nominative Open](http://open.mapquestapi.com/nominatim/) uses "json_callback" instead of "callback".
+
+If you want to use `eval` to parse JSON in older browsers you need to pass an option `evil` set to something truthy.
+
+If you want to be able to load stuff from the file system (with appropriate custom flags set) set local to true.
+
+Gives off three events `data:loading`, `data:progress` and `data:loaded`.
+
+- `data:loading` fires before we start downloading things, note if the constructor is given a url it won't wait to be added to the map
+to start downloading the data, but it does do an async wait so you have time to add a listener to it (and so [leaflet.spin](https://github.com/makinacorpus/Leaflet.Spin) will work with it).
+- `data:progress` is called each time a file is downloaded and passes the downloaded geojson as event data.
+- `data:loaded` is called when all files have downloaded, this is mainly different from `data:progress` when you are downloading multiple things.
+
+You can also add a middleware function which is called after you download the data but before you add it to leaflet:
+
+```javascript
+var geojsonLayer = L.geoJson.ajax("route/to/esri.json",{
+    	middleware:function(data){
+        	return esri2geoOrSomething(json);
+    	}
+    });
+```
+
+addUrl does not clear the current layers but adds to the current one,  e.g.:
+
+```javascript
+var geojsonLayer = L.geoJson.ajax("data.json");
+geojsonLayer.addUrl("data2.json");//we now have 2 layers
+geojsonLayer.refresh();//redownload the most recent layer
+geojsonLayer.refresh("new1.json");//add a new layer replacing whatever is there
+```
+
+last but now least we can refilter layers without re adding them
+
+```javascript
+var geojsonLayer = L.geoJson.ajax("data.json");
+geojsonLayer.refilter(function(feature){
+    return feature.properties.key === values;
+});
+```
+
+Behind the scenes are two new classes L.Util.ajax = function (url) for same origin requests and L.Util.jsonp = function (url,options) cross origin ones. Both return promises, which have an additional abort method that will abort the ajax request.
+
+```js
+L.Util.ajax("url/same/origin.xml").then(function(data){
+	doStuff(data);
+});
+//or
+L.Util.jsonp("http://www.dif.ori/gin").then(function(data){
+	doStuff(data);
+});
+```
+
+In related news `L.Util.Promise` is now a constructor for a promise, it takes one argument, a resolver function.
+
+Some of the jsonp code inspired by/taken from [this interesting looking plugin](https://github.com/stefanocudini/leaflet-search) that I have failed to make heads nor tails of (the plugin, not the jsonp code)