Remove overreaching rescue clauses

These belong in the adapters. Raising exceptions in situations like this
is database-specific anyway since different databases handle these cases
differently. For example, Postgres doesn't chuck an error when the field
being incremented is null, but MongoDB does.
Add integration specs for any?/none? on query attrs
Stringify attribute names

Previously, if an attribute was passed in as a symbol (as is most
likely), #to_s would return the symbol instead of a string.
Add type to attribute in integration spec
Compare name attribute instead of string value

The string value was being compared to a symbol, which was kinda weird.
Whoever wrote that code clearly doesn't know what they're doing. Just
please don't run git blame on it.
Remove unnecessary cleanup

There is an after callback that drops the table. There is no need to
drop the index.
Add expectation to check that an index was added