Inline image fixes

- [new] Takes advantage of screen width to display wider images.
- [fixed] Horizontal spacing of inline images follows the new grid (10px/20px)

### Before (mobile landscape and above)
![screen shot 2013-09-09 at 14 52 28](https://f.cloud.github.com/assets/85783/1107195/08c5dff6-1958-11e3-9c95-c0fad896c9df.PNG)

### After (mobile landscape and above)
![screen shot 2013-09-09 at 14 55 59](https://f.cloud.github.com/assets/85783/1107197/163c82fc-1958-11e3-965e-8fa4050b7828.PNG)


And a homemade gif… /cc @oncletom
![hacking-kaelig-oncletom](https://f.cloud.github.com/assets/85783/1107212/7b9d7868-1958-11e3-8d29-85d49b6369c1.gif)