doc: mention that go tools is needed to access some tool
doc: mention that go tools is needed to access some tool

Change-Id: I020cd3d10a441ba4047800fdf4f93433c458398a
Reviewed-on: https://go-review.googlesource.com/43717
Reviewed-by: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>

josharian/go,derekmarcotte/go,codestation/go,ImJasonH/go,vsekhar/elastic-go,codestation/go,golang/go,Cofyc/go,CAFxX/go,derekmarcotte/go,christopher-henderson/Go,cloudflare/go,Cofyc/go,derekmarcotte/go,polyverse-security/go,ImJasonH/go,nawawi/go,polyverse-security/go,vsekhar/elastic-go,akutz/go,josharian/go,ImJasonH/go,vsekhar/elastic-go,ImJasonH/go,Cofyc/go,akutz/go,cloudflare/go,nawawi/go,josharian/go,Cofyc/go,codestation/go,cloudflare/go,Cofyc/go,akutz/go,derekmarcotte/go,cloudflare/go,vsekhar/elastic-go,nawawi/go,CAFxX/go,codestation/go,golang/go,akutz/go,josharian/go,codestation/go,cloudflare/go,ImJasonH/go,nawawi/go,josharian/go,derekmarcotte/go,codestation/go,ImJasonH/go,cloudflare/go,vsekhar/elastic-go,CAFxX/go,nawawi/go,nawawi/go,golang/go,josharian/go,polyverse-security/go,golang/go,polyverse-security/go,polyverse-security/go,derekmarcotte/go,golang/go,CAFxX/go,Cofyc/go,akutz/go,josharian/go,Cofyc/go,derekmarcotte/go,josharian/go,vsekhar/elastic-go,akutz/go,golang/go,golang/go,CAFxX/go,ImJasonH/go,golang/go,polyverse-security/go,codestation/go,polyverse-security/go,akutz/go,ImJasonH/go,cloudflare/go,akutz/go,cloudflare/go,vsekhar/elastic-go,CAFxX/go,polyverse-security/go,codestation/go,vsekhar/elastic-go,nawawi/go,Cofyc/go,nawawi/go,CAFxX/go,derekmarcotte/go,CAFxX/go