remove requirement to quote command if using shell alias
remove requirement to quote command if using shell alias

Previously, when using a shell alias for the command, the alias and args
needed to be quoted so it would be properly handled by os.Exec().  Now,
if we think we're trying to use an alias, automatically pass the desired
command in a way which won't require the user to quote the command

mmmorris1975/go-aws-runas,mmmorris1975/aws-runas,mmmorris1975/aws-runas,mmmorris1975/aws-runas,mmmorris1975/aws-runas,mmmorris1975/aws-runas