doc: clarify that GOROOT is only necessary for non-standard install locations

[gopherbot]

by nsan1129:

http://golang.org/doc/install needs to be changed to reflect the most current best
practice (and the practice that practically every other document advises), to set the
GOPATH environment variable but not GOROOT. This is a huge potential source of confusion
for newcomers to the language.

[gopherbot]

Comment 1 by nsan1129:

I've just carefully reread the directions on that page and I realize that the directions
are actually only related to the installation of go. Perhaps a more explicit description
to that effect should occur in the sentence directly above the code snippet with the
export statements?

[adg]

Comment 2:

I agree, if you're skimming you won't notice.

Owner changed to @adg.

Status changed to Accepted.

[gopherbot]

Comment 3:

We keep getting people asking about this on IRC, clearly having missed the "If you do
this" part.

[adg]

Comment 4:

This issue was closed by revision c497c9e.

Status changed to Fixed.

[adg]

Comment 5:

This issue was closed by revision 99800d9524cd.