title: merging ruby hash with array of values into another hash with array of values
body: <p>I can't seem to find anywhere that talks about doing this.</p>
  
  <p>Say I have a hash <code>{"23"=&gt;[0,3]}</code> and I want to merge in this hash <code>{"23"=&gt;[2,3]}</code> to result with this hash <code>{"23"=&gt;[0,2,3]}</code></p>
  
  <p>Or how about <code>{"23"=&gt;[3]}</code> merged with <code>{"23"=&gt;0}</code> to get <code>{"23"=&gt;[0,3]}</code></p>
  
  <p>Thanks!</p>