Remove conflicting short flag -h

[pschultz]

The -h flag shows the usage message instead of working like --host:

$ beanstool stats -h localhost:11300
Usage:
  beanstool [OPTIONS] stats [stats-OPTIONS]

Help Options:
  -h, --help       Show this help message

[stats command options]
      -t, --tubes= tubes to be listed (separated by ,). By default all are listed
      -h, --host=  beanstalkd host addr. (default: localhost:11300)
[snip]

beanstool stats --host localhost:11300 works as expected. This PR removes -h as alternative for --host.