Get methods

[xogeny]

Would you accept a pull request with some useful Get methods for specific types ala jason?

The point is that gabs seems to be good for building up data in Containers and jason seems to be good at reading values. But it is useful to have both (in one package). So I would propose adding basically the same methods Get* that jason has.

Comments?

[Jeffail]

Hey @xogeny, after a lot of thought I've decided to leave the API as it is for now. I'd rather encourage users to stick to the native go way of v, ok := gabs.Data().(string) rather than add a gabs.String() method, since it also encourages users to opt for type select statements etc.