Update karma-webpack depency to fix confusing error

Using karma-webpack-plugin 1.0.0 lead to the following error from grunt
test immediately after generating.  I found the following fix in
karma-webpack that had not been included in karma-webpack-plugin because
it has since become karma-webpack.

INFO [PhantomJS 1.9.7 (Mac OS X)]: Connected on socket 33J3dAUsvdMT6Io38nxm with id 51124214
PhantomJS 1.9.7 (Mac OS X) ERROR
  TEST RUN WAS CANCELLED because this file contains some errors:
      /Users/brandon/Workspace/eventlist/test/spec/components/EventlistApp.js