Option to disable MySQL to JS types conversion

[Sannis]

Add option for res.fetch*() methods that disables MySQL to JavaScript types conversions.

[Sannis]

Also this was suggested and discussed in #110.

[Sannis]

Also a good alternative: mysqljs/mysql#259. I need to write a benchmark to decide.

[Mrono]

If you disable type casting in node-mysql you must cast everything manually