fix(karma-webpack): don't include the os.tmpdir (output.publicPath) (#338)

Author: pat841

src/karma-webpack.js

@@ -81,7 +81,7 @@ function Plugin(
       '/'
     );
     webpackOptions.output.publicPath = path.join(
-      os.tmpdir(),
+      '/',
       '_karma_webpack_',
       publicPath,
       '/'
@@ -211,7 +211,7 @@ function Plugin(
   compiler.hooks.invalid.tap(this.plugin, invalid.bind(this));
 
   webpackMiddlewareOptions.publicPath = path.join(
-    os.tmpdir(),
+    '/',
     '_karma_webpack_',
     '/'
   );