Add safeCopy to Fact
Moved compression settings to common lib
SnapshotMr.scala -> mr.scala
Add mr context object for keeping track of tmp and dist cache paths
Fixes from pull request

- Compress now only takes a job object and not a configuration
- MrContext is now a case class and all the lazy vals have been changed
- ThriftCache has one instance of serializer/deserializer instead of creating a new one per call to push/pop
Merge pull request #54 from raronson/russ_wip

Some of the ivory cleanup work