Job role update

I needed to add the current Javascript engineer position and I noticed that a few of the other descriptions didn't make sense (mentioning Java and guardian.co.uk for example).

I haven't touch the client-side dev role but I've tried to update all the others.

Call me old-fashioned, but I expect capitals in job titles, and [everybody](http://developers.nytimes.com/careers/) [else](https://gds.blog.gov.uk/jobs/) [does](https://about.twitter.com/careers/locations/london) [it](http://careers.mozilla.org/en-US/listings/).