Binarypackage for step-cli

Should revisit and add binary package at some point, probably best to wait until upstream has refactored dependencies

• github.com/smallstep/assert

needed for binary (step-cli):

• github.com/ThomasRooney/gexpect
• github.com/smallstep/certinfo
  • github.com/google/certificate-transparency-go
• github.com/smallstep/zcrypto (-> 5 deps)
• github.com/smallstep/zlint
• go.mozilla.org/pkcs7 (-> base on fullsailor/pkcs7 instead?)
• github.com/SSLMate/go-pkcs12

refactor package

• instead of embedding pkg/blackfriday, package should build on blackfriday in the repos

not needed

• github.com/Microsoft/go-winio for windows build
• github.com/golangci/golangci-lint nur linter
• github.com/samfoo/ansi provided by golang-github-mgutz-ansi-dev (in unstable)