feat: add --version (guyfedwards#56)

use ldflags main.version from goreleaser

fixes guyfedwards#52

fix: make module v2 (guyfedwards#55)

fixes issue with go install not pulling latest version
and allows for bsd port

fixes guyfedwards#54, guyfedwards#51

fix: toggle read (guyfedwards#50)

The "Toggle read" functionality marked items as read, but never as
unread.