Crate

- Fix datetime parsing that didn't work with crate >= 0.18.4 due
to the fixed datetime mapping

- Document `count()` and `group_by()` support

================

- http keepalive support

- uppercase command support for crash

- fixed python3.3 compatibility issue in crash

================

- the `crash` crate cli supports multiple line commands and auto-completion now,
commands are delimited by a semi-colon.

- the `crash` crate cli displays the status and, if related, the row count on every command now.

- `DateTime` and `Date` can now be nullable

- Fix an ORM error with the `Craty` type and where the `update`
statement wasn't correctly generated