update dependencies (#76)

README: fix replace directive

go.mod: upgrade to go-internal latest

do not use go list to find go.mod file (#56)

cmdget: support +incompatible tags with -vcs

README.md - Clarify 'gohack get' with and without the -vcs option (#47)

main.go - Clean up documentation of 'status' and remove mention of 'diff' command that doesn't exist (#48)

add missing docs (#43)

main: fix definition and implementation of relative GOHACK (#49)

travis: fix travis config (#50)

Allow relative paths in GOHACK env var (#45)

Merge pull request #41 from rogpeppe/suggest_gobin_install_alternative

README: suggest gobin as an install alternative.

Merge pull request #37 from rogpeppe/018-update-go-internal

use github.com/rogpeppe/go-internal@v1.0.0