core::tuple should have methods aswell/instead of functions

[Dretch]

core::tuple has first, second and swap functions. I think it would be nice to have these as methods.

Possibly the functions should be removed and replaced entirely with the methods?

I can push the (trivial) code for this change, if it is desired?

[z0w0]

Sounds like a good idea.

[catamorphism]

0487663 should take care of this.