Tidy up dropdowns on live blogs

Fixes a few issues/bugs on liveblog drop downs (up to desktop breakpoints), namely overlapping with page margins, padding around content and collapsed menu appearance. Picture: 

Open before:
![screen shot 2014-09-26 at 13 12 09](https://cloud.githubusercontent.com/assets/813383/4420245/bfd1f81a-4576-11e4-9b29-2842679444ec.png)

Open after:
![screen shot 2014-09-26 at 13 12 20](https://cloud.githubusercontent.com/assets/813383/4420248/ccdccea4-4576-11e4-83b4-149cd90500d5.png)

Closed before:
![screen shot 2014-09-26 at 13 12 30](https://cloud.githubusercontent.com/assets/813383/4420249/d21d1c20-4576-11e4-8d3b-6a106b4f56ca.png)

Closed after:
![screen shot 2014-09-26 at 13 12 44](https://cloud.githubusercontent.com/assets/813383/4420256/d77b77b6-4576-11e4-95dc-524400c3fe3c.png)

A second PR will be needed to fix borders on facia containers, so that they extend to the full width of the page, as they do above tablet breakpoint.

/cc @mattosborn