Get rid of tai64n timestamps, and knowledge of timestamp format in eliot.filter.
Merge remote-tracking branch 'refs/remotes/origin/serialization-in-destinations-44' into no-tai64n-51
An example of outputting to stdout (useful for testing eliot.filter).
Document timestamp field.
Fix pyflakes error.
Address review comment: more details on the format of timestamps.
Merge remote-tracking branch 'refs/remotes/origin/master' into no-tai64n-51
News entry for timestamp format change.
Merge pull request #56 from hybridcluster/no-tai64n-51

No tai64n in timestamp fields.

Fixes #51.