Update golint install instructions
Update golint install instructions

Summary:
These are the instructions from https://github.com/golang/lint.

The fetch location changed to `golang.org/x/lint/golint` from `github.com/golang/lint/golint`.
`-u` tells go to update the package and its deps if they exist.
`-u` Shouldn't strictly be necessary, but figured we might as well follow the instructions from `golint`.

Test Plan:
Enable golint without having it installed.
Ensure that the install instructions now show the new location.

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: Korvin

Differential Revision: https://secure.phabricator.com/D21552

codelabs-ch/arcanist,codelabs-ch/arcanist,codelabs-ch/arcanist,phacility/arcanist,Khan/arcanist,phacility/arcanist,phacility/arcanist,phacility/arcanist,Khan/arcanist,Khan/arcanist,codelabs-ch/arcanist,Khan/arcanist,phacility/arcanist,codelabs-ch/arcanist