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
Memoize certain config. props. in Uploader
Memoize topic-partition forget secs. in MessageReader
Add “NoReloadingStrategy” for SecorConfig

Currently there’s a lot of time spent reloading the configuration file
from disk, which is a pretty nifty mechanism, but it only applies to
a certain (not really well-defined) set of configuration parameters, and
it should either apply to all configuration parameters, or non. The
latter is covered by this commit.