main: Remove dependency on pflag library
main: Remove dependency on pflag library

The only advantage was that it allowed us to define a shorthand (`-v`)
for the `--verbose` option, but we barely used that flag anyway, so the
additional overhead wasn't worth it.

Closes #78.

Signed-off-by: Lorenzo Manacorda <86995a091f8a1385082bd10715048b52ee386a6a@kinvolk.io>

kinvolk/habitat-operator,kinvolk/habitat-operator