This is close to a complete rewrite, as the content was pretty old.

The CL includes links to the Wiki for information about companies
using Go, a new section about IDEs and editors¹, and a restatement
of the foreign function interface story. It also modernizes and
expands a little on the use of Go inside Google.

¹ Ed is the standard editor.

Change-Id: I5e54aafa53d00d86297b2691960a376b40f6225b
Reviewed-on: https://go-review.googlesource.com/123922Reviewed-by: Ian Lance Taylor <iant@golang.org>