First attempt at "sample" operator. Should probably use "interval"
operator instead of an internal clock. Also still needs tests!
Merge branch 'interval' into sample
Switched sample from internal clock to using the interval operator
Added a unit test against the sample operator
Merge branch 'master' into sample
added missing linebreak
minor renaming and removing unnecessary warning suppression again
Added value class wrapping timestamped values
Added toString to Timestamped
added copyright text to Timestamped class, added timestamp operation, reusing mapping
Removed superfluous null check
Added `timestamp` method to `Observable`, too.
Merge remote-tracking branch 'parent/master' into timestamp
Merged with master from Netflix repo.
Merge branch 'master' into sample
Added sample methods to observable.
Update CHANGES.md
Fix multiple subscription bug on operation filter

A new subscription must be created on every subscribe call, otherwise any
subscribe call after the first directly fails.
Merge pull request #253 from Treora/master

Fix multiple subscription bug on operation filter
Merge pull request #248 from jmhofer/sample

Implemented Sample Operation