talks/2014/names: revise slides on local variables

I was overzealous about short local variable names.
On reflection I think my advice was too strong, and
the example I gave was hard even for me to read.

Change-Id: I3c300b95ac0453b9b5d1cfcd1e167965b643c817
Reviewed-on: https://go-review.googlesource.com/78135
Reviewed-by: Rob Pike <r@golang.org>