title: RSpec, Appium: provide desired capabilities from CLI
body: <p>I am using this official Appium page <a href="http://appium.io/docs/en/writing-running-appium/default-capabilities-arg/" rel="nofollow noreferrer">http://appium.io/docs/en/writing-running-appium/default-capabilities-arg/</a></p>
  
  <p>and I want to override the capabilities which are provided in <code>spec_helper.rb</code> this way </p>
  
  <pre><code>rspec --default-capabilities spec/test_data/new_caps.json spec/cli_test/cli_test_spec.rb
  </code></pre>
  
  <p>but it is giving me error <code>invalid option: --default-capabilities</code>.</p>
  
  <p>Appium server already running in the background. </p>
  
  <p>What am I doing wrong here?</p>