Improve edition history and notes

* [ ] Developer review
* [ ] Product review
* [ ] Content designer review

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https://www.agileplannerapp.com/boards/173808/cards/6039

* Make edition history and notes full width with improved legibility
* Make scanning history and changes easier with larger headings and timestamps that follow the style guide
* Tweak copy to be inline with style guide
* Move notes forms behind modals to match workflow behaviour and to avoid obscuring the more important history view

Before:
![screen shot 2014-10-09 at 11 44 44](https://cloud.githubusercontent.com/assets/319055/4574960/afb40a38-4fa1-11e4-88e3-23aafc342d43.png)

After:
![screen shot 2014-10-09 at 11 45 47](https://cloud.githubusercontent.com/assets/319055/4574961/b3217f34-4fa1-11e4-95f3-eeffffaa90f2.png)

![screen shot 2014-10-09 at 11 46 08](https://cloud.githubusercontent.com/assets/319055/4574962/b34adf50-4fa1-11e4-9d3c-b0078845745b.png)

![screen shot 2014-10-09 at 11 46 24](https://cloud.githubusercontent.com/assets/319055/4574963/b3550746-4fa1-11e4-8cd9-74834a168550.png)