Udpate karma version in package.json

[hongyanh]

When I was trying to use gulp to build the project, there is a dependency issue cased by outdated karma package:

Store.prototype.__proto__ = EventEmitter.prototype;
                                         ^
TypeError: Cannot read property 'prototype' of undefined

After updated karma version from 0.12.16 to 2.0.4 in package.json file, the error is gone when I build the project.

[andrewkittredge]

Updating to karma 3.0.0 also works.