fix PriorityScheduler bug
Merge pull request #90 from manuzhang/at_least_once

fix OffsetManager update and checkpoint bug
Merge pull request #91 from manuzhang/at_least_once

fix creating checkpoint topic conflicts
each TopicAndPartition checkpoints to its own Kafka topic
split consumer thread from main loop
don't load starting offsets when launching an application for the first time
handle the condition when all TopicAndPartitions have no more messages to fetch
make consumer queue size configurable
remove obsolete file
Merge pull request #92 from manuzhang/at_least_once

make consumer run in a separate thread from main loop
add checkpoint id as a work around for nonpersistent application id
Merge remote-tracking branch 'upstream/master'
close thread and change no message log to debug level
reallocate resource if executor launch rejected
KafkaCheckpointManager uses the low level Kafka consumer and consumes only once
Merge pull request #93 from huafengw/error_recovery

Error recovery
Merge remote branch 'upstream/master' into add_test
Merge remote branch 'origin/at_least_once' into add_test
make specs2 work
transaction interface refactor