Query struct should not store types

[fishcakez]

Mariaex never uses types stored in the query struct. Instead it encodes parameters using Elixir types and lets MySQL cast the terms, getting a database error if it can not. On decode it uses the column description that is sent immediately before the rows. By storing and checking these types we introduce errors where we don't need to.

This raise was introduced in #145.

[fishcakez]

This was fixed in eb08f78.