title: Unable to install gems with rbenv
body: <p><strong>rbenv</strong></p>
  
  <p><code>$ ruby -v</code> <br>
  ruby 1.9.3p0 (2011-10-30 revision 33570) [x86_64-linux]<br>
  <code>$ gem -v</code>  <br>
  1.8.23</p>
  
  <p><code>$ gem install rails</code>  <br>
  ERROR:  Loading command: install (LoadError)<br>
      cannot load such file -- zlib<br>
  ERROR:  While executing gem ... (NameError)<br>
      uninitialized constant Gem::Commands::InstallCommand</p>
  
  <p><code>$ gem install railties</code>  <br>
  ERROR:  Loading command: install (LoadError)<br>
      cannot load such file -- zlib<br>
  ERROR:  While executing gem ... (NameError)<br>
      uninitialized constant Gem::Commands::InstallCommand</p>
  
  <p>I spent hours looking for answers...</p>
  
  <p>Also installed <code>zlib1g-devel</code> but still cant install rails..</p>