Offline Mode!

This commit adds offline mode functionality. Basically,
if we don't have network in DetailView, don't try to load
from the network, just use what we have. Similarily,
don't try to sync to MAL with no connection, just save
locally.

When connection is restored (detected by the Home activity),
first we write any records marked dirty to MAL, then sync
as usual.

Also, the Search and Sync options vanish with no connection
and return when connection returns.

Oh, and I converted all the Toasts to Croutons. They look
much nicer now.