title: Python Click command doesn't recognize options
body: <p>I am trying to register command-line options in Click. Everything is working fine until I add the <code>params</code> argument to the constructor. </p>
  
  <pre><code>class InitCommand(click.Command):
      def __init__(self):
          super().__init__(
              name='init',
              short_help='Initialize the needed scaffolding.',
              help='something helpful, but longer',
              # params=[]    ### &lt;-- Works fine
              params=[click.Option('--force', default=False)]
          )
  </code></pre>
  
  <p>I get the following error:</p>
  
  <pre><code>Traceback (most recent call last):
    File "/usr/local/bin/aquapy", line 11, in &lt;module&gt;
      load_entry_point('aquapy-cli', 'console_scripts', 'aquapy')()
    File "/usr/local/lib/python3.6/site-packages/pkg_resources/__init__.py", line 561, in load_entry_point
      return get_distribution(dist).load_entry_point(group, name)
    File "/usr/local/lib/python3.6/site-packages/pkg_resources/__init__.py", line 2631, in load_entry_point
      return ep.load()
    File "/usr/local/lib/python3.6/site-packages/pkg_resources/__init__.py", line 2291, in load
      return self.resolve()
    File "/usr/local/lib/python3.6/site-packages/pkg_resources/__init__.py", line 2297, in resolve
      module = __import__(self.module_name, fromlist=['__name__'], level=0)
    File "/Users/******/__main__.py", line 3, in &lt;module&gt;
      from .bootstrap import main
    File "/Users/******/bootstrap.py", line 17, in &lt;module&gt;
      main.add_command(InitCommand())
    File "/Users/******/commands/init_command.py", line 10, in __init__
      params=[click.Option('--force', default=False)]
    File "/usr/local/lib/python3.6/site-packages/click/core.py", line 1460, in __init__
      Parameter.__init__(self, param_decls, type=type, **attrs)
    File "/usr/local/lib/python3.6/site-packages/click/core.py", line 1266, in __init__
      self._parse_decls(param_decls or (), expose_value)
    File "/usr/local/lib/python3.6/site-packages/click/core.py", line 1533, in _parse_decls
      raise TypeError('Name defined twice')
  TypeError: Name defined twice
  </code></pre>