Add dt_type support for Mango::BSON::Time

[oliwer]

This commit adds support for the Mongo::BSON::Time type, which
will significantly simplify the transition from Mango::BSON to
MongoDB's BSON.

[xdg]

Thanks. I'm going to hold off applying these until after I ship v1.0.0, as I've been waiting on green smoke tests for that and don't want to introduce new code before shipping the new stable.

I think all your suggested changes are only additions to behavior, not changes, which is fine to release later in v1.2.0. If you think otherwise, please let me know ASAP.

[coveralls]

Coverage decreased (-0.2%) to 86.935% when pulling cc1abe5 on oliwer:dt_mango into 3ec51dc on mongodb:master.

[oliwer]

Well, it depends when do you plan to release v1.2.0? I'm gonna start a new Mango branch with only the minimal API changes needed to be compatible with BSON. This requires of course that my 2 pull requests are merged. I would like to do that as soon as possible so I would really prefer if these commits were included in v1.0.0. I promess there is no bug :p

[xdg]

I'll release a v1.1.0-TRIAL ASAP after v1.0.0 and we can iterate your PR there. I have no problem shipping v1.2.0 as early as next week if it looks good and smokes well.

[oliwer]

Oops. Things got confused in my head. This is what I actually plan to do:

• release Mango 1.30 this week with only a few api deprecations and NOT depending on BSON
• wait at least 3 weeks to give time to users to adapt
• release Mango 2.00 which uses BSON and requires my commits

So there is actually no big hurry. Sorry about that.

[xdg]

Rebased, line indent fixed, and merged as 5f5982c.

Once we agree on from_epoch, I'll ship v1.1.0-TRIAL and you'll have
something you can work from for Mango.