Add support for explicit type conversion to double & int
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.
Merge pull request #63 from kenahoo/master

Add support for explicit type conversion to double & int