Use UTC time for BSON value_transform
Use UTC time for BSON value_transform

The schema creates `timestamp without timezone` fields, which will discard any
timezone information present in the `to_s` output of the timezone object. This ensures
that the proper time is stored in postgresql.

E.G. (where "5555f7e2" is the first 8 characters of a mongodb ObjectId, representing
the time at which it was created):

`ruby -e 'puts(Time.at "5555f7e2".to_i(16))'`
2015-05-15 09:42:58 -0400

`ruby -e 'puts((Time.at "5555f7e2".to_i(16)).utc)'`
2015-05-15 13:42:58 UTC

iCHEF/mosql