Fix travis build
Fix travis build

Macs don't support nanosecond precision (it appears to perhaps be
microprecision?). Linux does. Postgres timestamps are microsecond
precision. If we send it a value with nanosecond precision, it'll change
when we round trip.

sgrif/diesel,cascalheira/diesel,diesel-rs/diesel,diesel-rs/diesel,mcasper/diesel,mcasper/diesel,cascalheira/diesel,tohou/diesel,SoftwareWarlock/diesel,SoftwareWarlock/diesel,sgrif/diesel,tohou/diesel