Support lower res with responsive logviewer (1042466)

This work fixes Bugzilla bug [1042466](https://bugzilla.mozilla.org/show_bug.cgi?id=1042466).

Thanks to @camd's stellar work which I am just facilitating by this branch and PR. This allows the user to view the structured log and all its contents and functionality with browser dimensions well below the implied/requested 960px. The one minor issue is the left hand run-data content not 'sliding over' as nicely as it could and log steps being clipped *if* successful steps are displayed, but that is the only minor downside I've seen. I haven't yet figured out that mystery or if it is even possible to address it given the existing functionality requirements.

This is a screen grab of the support it provides

![flowingstructuredlog_aug27_](https://cloud.githubusercontent.com/assets/3660661/4065477/087a0210-2e1b-11e4-9b33-262cc1cbcb2f.jpg)

I've tested a variety of workflows throughout the work, and other than the issue mentioned above, everything seems fine.

Tested on Windows:
FF Release **31.0**
Chrome Latest Release **36.0.1985.143 m**

Adding @camd @jeads and @maurodoglio for visibility.