Fix html-webpack-plugin warning

Not returning the result in the callback is deprecated in html-webpack-plugin.

Author: silvenon

index.js

@@ -16,8 +16,8 @@ HtmlWebpackWrapHtmlPlugin.prototype.apply = function(compiler) {
 				htmlPluginData.html += "\n" + options.after;
 			}
 
-			callback();
+			callback(null, htmlPluginData);
 		});
 	});
 };
-module.exports = HtmlWebpackWrapHtmlPlugin;
+module.exports = HtmlWebpackWrapHtmlPlugin;