Add TypeScript definitions for tcomb-form

[RedRoserade]

This adds TypeScript definitions for tcomb-form, based on the Guide.

A devDependency on @types/react was added for the Form component and the other Component classes.

Similar to the type definition for tcomb-validation, https://github.com/gcanti/tcomb-validation/pull/63, this extends the tcomb module, adding getTcombFormFactory and getTcombFormOptions to t.Type<T>.

I am, however, not sure if the type definitions are 100% complete or accurate. I'd appreciate your feedback to improve them.

[gcanti]

@RedRoserade this is great, thanks for taking the time to write this definitions

[bialasik]

Why it's still doesn't merged?

[gcanti]

My bad, there was a pending review which I didn't submit at the time, sorry @RedRoserade

[marcodafonseca]

Can the above change request please be acted on? It would be really helpful to have Typescript definitions enabled.