Typescript support

Hello @gregnb,

I'm a typescript user and I wanted to know if you are interested in typescript support for this component ? Material-ui-next have a support for each component so I think it can be nice to have for the MUIDatatables too. I never did a [declaration file](https://www.typescriptlang.org/docs/handbook/declaration-files/introduction.html) before, but I think it can be a nice exercice for me so if you want i'm interested to write it.