Change timeout for pusher fallback to 30s

We have a bug that results in sending unneeded ajax queries on missing
log parts. I'm working on a fix, but it may take a while, because I want
to refactor a few parts of the app instead of putting more hacks on
legacy code. To help with the situation I'm increasing timeout for
pusher fallback.
Revert "Merge pull request #308 from rwjblue/update-ember"

After upgrading ember to 1.8.1 tests pass, but I found a few cases where
things break (for example when navigating between certain routes). I'm
reverting for now.

This reverts commit fa5e9179af98bb01d4b28f3e12bd1fa82b25ba97, reversing
changes made to 978c88712375418bb2e5861fd9b91a3115520d52.
Make pusher log fallback configurable and disable it by default