[TH] timestamps function
[TH] add timestamps from entity-id

Also add a unique schema attribute so that the
timestamps from attribute test has a unique field
to work from. Not strictly required, but is the
suggested way to work with it.
[TH] make attribute value timestamps fn deterministic

Now only will return timestamps if the attribute is
unique.
[TH] entity id only form of timestamps
Merge branch 'master' into timestamps
Merge pull request #2 from turbovote/timestamps

[TH] timestamps function