Streamable

[Brian Goetz]

I am considering dropping the Streamable interface.  Currently the only 
implementor is Collection, and all of the other stream-bearing methods 
are serving up specialized streams (chars(), codePoints(), lines(), etc) 
with a method name that is more suitable than "stream".  So I think we 
should drop Streamable and leave the stream() / parallel() methods on 
Collection (or possibly move them up Iterable).

Also still leaning towards renaming parallel() to parallelStream().