title: Unable to set adapter as ffi
body: <p>In automation, I'm trying to handle windows popup using rautomation. I've following gems installed:</p>
  
  <pre><code>ffi (1.9.0 x86-mingw32, 1.8.1 x86-mingw32)
  rautomation (0.9.2)
  </code></pre>
  
  <p>I tried following:</p>
  
  <pre><code>require 'rautomation'
  window = RAutomation::Window.new :title =&gt; "Opening rautomation-0.9.2.gem"
  
  =&gt; #&lt;RAutomation::Window:0x2c4bd30 @adapter=:win_32, @window=#&lt;RAutomation::Adapter::Win32::Window:0x2ccd7c8 @container=#&lt;RAutomation::Windo
  w:0x2c4bd30 ...&gt;, @locators={:index=&gt;0, :title=&gt;"Opening rautomation-0.9.2.gem"}&gt;&gt;
  </code></pre>
  
  <p>By default, adapter isn't set to ffi (It's set to win_32, I'm using windows machine) and hence I tried to set it to ffi:</p>
  
  <pre><code>window.hwnd
  =&gt; 1508532
  new_window = RAutomation::Window.new :hwnd =&gt; 1508532, :adapter =&gt; :ffi
  </code></pre>
  
  <p>But it's resulting into following error:</p>
  
  <pre><code>NameError: uninitialized constant RAutomation::Adapter::Ffi
          from C:/Ruby193/lib/ruby/gems/1.9.1/gems/rautomation-0.9.2/lib/rautomation/window.rb:67:in `const_get'
          from C:/Ruby193/lib/ruby/gems/1.9.1/gems/rautomation-0.9.2/lib/rautomation/window.rb:67:in `initialize'
          from (irb):7:in `new'
          from (irb):7
          from C:/Ruby193/bin/irb:12:in `&lt;main&gt;'
  </code></pre>
  
  <p>Following are my questions:</p>
  
  <ol>
  <li>Why adapter isn't set to ffi even though ffi installed on my machine?</li>
  <li>How to resolve the error that I faced when I tried to set adapter to ffi? (For this I had also done: set RAUTOMATION_ADAPTER=ffi still it's not working)</li>
  </ol>