Next design iteration

We've added quite a lot of functionality to Twiddle over the past months. I think now would be a good time to look into how we can streamline all these functionalities and make the UI a bit cleaner.
### Formats
- [ ] Desktop 1440x1024
- [ ] Phone
- [ ] Tablet
- [ ] ...
### Low-level issues:
- #377, #132 And overall responsiveness
- #135 Show page title somewhere
- #108 Usage instructions (maybe put those in initial twiddle html)
### High-level stuff:
- I'd like to incorporate a statusbar or something similar to show status/progress
- I'd like to incorporate the filebrowser in a more elegant way
- I'd like there to be less UI (more content)
- #194 Review/improve all copy (like "Save to Github Gist")
- #153 More clarity on what twiddle you're working on (eg. "created by {user}")
### User stories
- An addon developer wants to demo an addon he/she has built
- An ember user want to try out a new addon
- An ember user want to demonstrate an issue with an addon
- An ember user want to demonstrate an issue in his/her app
- An ember user wants to play around with a new Ember feature
- An ember novice wants to play around with Ember
- The ember core team wants to demonstrate an Ember feature