title: Can't change RVM default
body: <p>I have problem changing the default ruby. Running OS X Lion.</p>
  
  <pre><code>macbook:~ work$ rvm list
  rvm rubies
  
  =* ruby-1.9.2-p290 [ x86_64 ]
     ruby-1.9.2-p318 [ x86_64 ]
  </code></pre>
  
  <p>As you can see, 1.9.2-p290 is the default.</p>
  
  <pre><code>macbook:~ work$ rvm use --default ruby-1.9.2-p318
  Using /usr/local/rvm/gems/ruby-1.9.2-p318
  macbook:~ work$ rvm list
  
  rvm rubies
  
  * ruby-1.9.2-p290 [ x86_64 ]
  =&gt; ruby-1.9.2-p318 [ x86_64 ]
  </code></pre>
  
  <p>After running rvm use --default ruby-1.9.2-p318, the Ruby changed, but default is still p290. And the next time I reopen a shell, the ruby used is p290.</p>
  
  <p>Any ideas?</p>
  
  <p>Thanks.</p>