Improved timing accuracy in the Registrar.

Review: https://reviews.apache.org/r/20897
Adds Netflix to #PoweredByMesos list.
Updated the 'contains' method in stout IntervalSet to support more
types.

Review: https://reviews.apache.org/r/20898
Added stream functions for stout Interval and IntervalSet.

Review: https://reviews.apache.org/r/20900
Introduced base64::encode/decode in stout.

Review: https://reviews.apache.org/r/20885