blacklist instead of whitelist files for npm

.npmignore

@@ -0,0 +1,3 @@
+leaflet-side-by-side.js
+leaflet-side-by-side.min.js
+screencast.gif

package.json

@@ -3,12 +3,6 @@
   "version": "1.1.1",
   "description": "Compare two Leaflet layers side by side",
   "main": "index.js",
-  "files": [
-    "index.js",
-    "range.css",
-    "range-icon.png",
-    "layout.css"
-  ],
   "browserify": {
     "transform": [
       "css-img-datauri-stream",