mulithread the uploading
Different log message for new partition

Currently when Secor starts consuming a “new” partition it logs a
warning that the offset for a given partition changed from -2 to
*something*, and I’d say that this particular scenario is expected and
shouldn’t generate a warning, but rather an info message that
consumption of a new partition has started.

For future reference, -2 means to start from the earliest available
offset and -1 means to start from the latest available offset, if I
remember correctly.
Merge pull request #40 from mthssdrbrg/offset-tracker-warn

Different log message for new partition in OffsetTracker
check upload policy less frequently
Merge pull request #35 from optimizely/check-upload-policy-less-frequently

Check upload policy less frequently
Add config support for kafka.partition.assignment.strategy

New feature that exists in kafka trunk, and basically what it does is
to distribute all partitions across all available consumer threads, so
that we actually can scale our “Secor” instances.