Add support for explicit type conversion to double & int
Fix hash ordering bugs

MongoDB requires the command to come before the arguments, but this
isn't guaranteed when passing a hashref to ->run_command. Use an
arrayref for commands with arguments to make sure the order gets right.
The code was mistakenly subtracting 1 minute from all DateTime::Tiny objects.  Fixed.

Also added tests to expose & confirm the fix, and needed a few
$db->drop() statements in there too, because it was fetching leftover
documents from previous tests.
Update docs to talk about DateTime::Tiny
Merge pull request #65 from kenahoo/date-docs

Update docs to talk about DateTime::Tiny
Merge pull request #63 from kenahoo/master

Add support for explicit type conversion to double & int
Merge pull request #64 from ilmari/fix-hash-ordering

Fix hash ordering bugs