Standardize DateTimes

[andrewkrug]

TypeError: datetime.datetime(2017, 3, 6, 19, 13, 16) is not JSON serializable occurs in python for warm_since and warm_for

Let's move them all to same format.

[tnem]

My vote is for using a long that's just time since epoch.

[andrewkrug]

@tnem I agree on this. It makes it way easier in elastic. But we should also make sure it's something that we can use as elastic's timestamp.

[jeffbryner]

Any reason not to do both? i.e. epoch and ISO formatted, human readable? ES will store either as epoch internally if the field is mapped as datetime, but it will help folks looking at the json if it's in both.

[andrewkrug]

@jeffbryner why not... as long as they can both go through json.dumps() and json.loads() I was getting errors with python's straight up "DateTime" type.