'polling' and 'new messages' flashing is now down by default poll hooks. after-poll hook gets passed new argumetnts num_total and num_inbox_total
HookContext#flash should fallback to log()

Not sure where it'd be used though.
Merge #70 'no-poll-flashing'

* Don't flash message when custom hooks before/after-poll are defined
* Pass num_total and num_inbox_total to after-pool hook
* Implement HookContext#flash