Increase expanded content max-height for mobile

Really, we want to not have to define a specific number and just unset the
max-height value. However, because the content transitions in, it needs a
numeric value to step against. On mobile, the content is much narrower,
which makes it much longer - hence the huge value used.
Merge pull request #2 from duncanhall/fix/mobile-expanded-content

Increase expanded content max-height for mobile