add assume method to quotas

can be overriden by quota classes to create new quotas from additional
assumptions.
add waiting_for_confirmation state to encoded files

* has to be enabled by configuration option
* confirm_encoding state machine event
add action_required file stage state

represent required user interaction for encoded files in
waiting_for_confirmation state.
count and notify about confirmable files
json endpoint for file encoding confirmation
begin confirm_encoding view
gitignore tmp dir
update state_machine_job gem

we need the need the new :if option for job results.
enforce encoding quota during encoding confirmation

* check quota on confirm
* json endpoint to query assumed quota state
display encoding confirmation summary in editor

check encoding confirmation remotely and render returned summary html.
pass confirm_encoding_jobs config option to editor
fetching meta data from zencoder

if confirm_encoding_jobs option is acitve, submit files to zencoder
with minimal output definition first to determine meta data.
separate file stage for fetching meta data
encoding_confirmed hook
move encoding hook invocations to state machine
save user confirming the encoding of a file
reconfirm encoding on retry
update CHANGELOG
Merge pull request #52 from tf/tf-confirm-encode

Add Configuration Option to Ask for Confirmation Before Encoding Files