feat(cli): abort `tk show` when stdout is being piped (#47)
feat(cli): abort `tk show` when stdout is being piped (#47)

* cmd/tk: abort `tk show` when stdout is being piped

Closes #3.

* cmd/tk: use existing interactive variable and add --dangerous-allow-redirect

--dangerous-allow-redirect bypasses check for running in an interactive
terminal. This flag should be passed if the user wants to redirect the
output of tk show to a pipe or a file.

grafana/tanka