Escape double quotes in JSON strings
Add support for more numeric types

- Integer and Fixnum are now BIGINT. Ruby Fixnums are 64-bit integers.
- Bignums and BigDecimals are stored as NUMERIC.
- Floats are stored as FLOAT (64-bit floating-point)
Don't allow double quotes in table names
Clean up automatic column insertion
Update expectations for column types
Cast numeric ids to numeric types
Keep first value when inserting multiple records
Remove superfluous `self`