fix(build): switch to cjs output for es5.

System output does not work at the current versions of TS and
system.js. Will revisit after upgrading TS.

Removes unused traceur tooling.

Closes #3974

modules/angular2/test/compiler/eval_module.ts

@@ -16,7 +16,12 @@ export function evalModule(moduleSource: string, moduleImports: string[][], args
     var modName = sourceImport[0];
     var modAlias = sourceImport[1];
     importModuleNames.push(modName);
-    moduleSourceWithImports.push(`var ${modAlias} = require('${modName}');`);
+    // Note: After transpilation to commonJS and loading this file in a browser
+    // using SystemJS, the loader might get confused by the presence of require,
+    // and attempt to load "+ modName +.js" !?!
+    // A simple string concat manages to prevent that, but that is one compiler
+    // optimaztion away from breaking again. Proceed with caution!
+    moduleSourceWithImports.push(`var ${modAlias} = require` + `('${modName}');`);
   });
   moduleSourceWithImports.push(moduleSource);