fix source mapsg

Author: guybedford

lib/loader.js

@@ -1056,6 +1056,8 @@ function logloads(loads) {
         var compiler = new traceur.Compiler();
         var options = System.traceurOptions || {};
         options.modules = 'instantiate';
+        options.sourceMaps = true;
+        options.filename = load.address;
         var output = compiler.stringToTree({content: load.source, options: options});
         checkForErrors(output);
 
@@ -1064,6 +1066,7 @@ function logloads(loads) {
 
         output = compiler.treeToString(output);
         checkForErrors(output);
+
         var source = output.js;
         var sourceMap = output.generatedSourceMap;