fix: add full support for webpack and angular

[lance]

Our webpack support needed some boosting to handle the use case presented by angular 5 and reported on here: #182

This pull request adds:

• Browser and headless testing using webpack instead of browserify
• Multiple webpack configurations: production, development and test
• Maintains compatibility with circuitBreaker as a global variable in the browser (WE SHOULD DEPRECATE THIS)

Do not merge yet. I would like to add some documentation on this to the README.md, but I just haven't had the chance. I also think we can change the examples (or add new ones) that use webpack to bundle the app.

connected to: #182

[coveralls]

Coverage increased (+0.3%) to 100.0% when pulling d1e2228 on 182-fix-browser-for-angular into 0178e95 on master.

[coveralls]

Coverage increased (+0.3%) to 100.0% when pulling 620ae79 on 182-fix-browser-for-angular into 0178e95 on master.