[Grace-core] Proposed Input spec

[James Noble]

> These look like methods on string streams — iterators over strings.    I agree that we need such a module.  

iterators or "streams" or something anyway. 

> These methods don’t seem to have anything to do with input or output.  An I missing something?

that - I guess - Kim want's em for an IO chapter in his book.
Now, that doesn't mean we have to bake 'em into the standard library

a few comment from me: 

>> type graceInput = {

type names need to be InitialCaps.
and (for the reasons above) GraceInput isn't a good name for this

perhaps SimpleInput or SimpleInputFile?

>>   nextNum(s:String)->Number

should be "nextNumber" (without the String) 

J