Improvements

[wheresrhys]

Just installed the component locally and found a few issues:

• [x] n-ui-foundations not installed in bower.json
• [x] the first time the button is clicked the text doesn't update. Maybe related to on line 48 of Newsletter.js you need to return? (Be careful to return promises from functions - sometimes things will basically work if you don't, but it can lead to unpredictability and hard to track down bugs)
• [x] I would rename the client directory to js. Client can have 2 meanings - all the client-side code (i.e. everything that gets loaded in the browser), which would suggest the styles should be in there too; or a library to communicate with an API. Neither of those descriptions match what is actually in there at the moment
• I wonder if the implementation could be simplified. Do you have any ideas on this? I wonder if it'd be simpler to reason about if feedback and newsletter classes were combined into one (Just something to think about, not to actually do anything about )
• [ ] Check that sensible tracking events are being sent (unfortunately the demo doesn't have tracking set up... but this is probably a general problem with all our demos). To check this try it out in the article app, and look for the ingest events in the network tab in dev tools

[fenglish]

I have done the top three on the PR above. I will come back and sort out the last one later (before this component is ready to use).