title: Cannot install the mechanize gem
body: <p>I only had ruby 2.0 on my system. I tried to install mechanize gem. It gave me an error which told me to install ruby devkit. I installed devkit as follows - Download the installer/extractor > extract devkit to c:\devkit > cd into c:\devkit > add the path c:\Ruby200-x64 into the config.yml file > <code>ruby dk.rb init</code> > <code>ruby dk.rb install</code>. Then I got the error below. How can this be fixed ?</p>
  
  <p><strong>config.yml file -</strong></p>
  
  <pre><code># Example:
  #
  # ---
  # - C:/ruby19trunk
  # - C:/ruby192dev
  #
  ---
  - C:\Ruby200-x64
  </code></pre>
  
  <p><strong>Error -</strong></p>
  
  <pre><code>C:\Ruby2Devkit&gt;gem install mechanize
  Temporarily enhancing PATH to include DevKit...
  Building native extensions.  This could take a while...
  ERROR:  Error installing mechanize:
          ERROR: Failed to build gem native extension.
  
      C:/Ruby200-x64/bin/ruby.exe extconf.rb
  checking for main() in -lstdc++... *** extconf.rb failed ***
  Could not create Makefile due to some reason, probably lack of necessary
  libraries and/or headers.  Check the mkmf.log file for more details.  You may
  need configuration options.
  
  Provided configuration options:
          --with-opt-dir
          --without-opt-dir
          --with-opt-include
          --without-opt-include=${opt-dir}/include
          --with-opt-lib
          --without-opt-lib=${opt-dir}/lib
          --with-make-prog
          --without-make-prog
          --srcdir=.
          --curdir
          --ruby=C:/Ruby200-x64/bin/ruby
          --with-stdc++lib
          --without-stdc++lib
  C:/Ruby200-x64/lib/ruby/2.0.0/mkmf.rb:434:in `try_do': The compiler failed 
  to generate an executable file. (RuntimeError)
  You have to install development tools first.
          from C:/Ruby200-x64/lib/ruby/2.0.0/mkmf.rb:519:in `try_link0'
          from C:/Ruby200-x64/lib/ruby/2.0.0/mkmf.rb:534:in `try_link'
          from C:/Ruby200-x64/lib/ruby/2.0.0/mkmf.rb:720:in `try_func'
          from C:/Ruby200-x64/lib/ruby/2.0.0/mkmf.rb:950:in `block in 
          have_library'
          from C:/Ruby200-x64/lib/ruby/2.0.0/mkmf.rb:895:in `block in 
          checking_for'
          from C:/Ruby200-x64/lib/ruby/2.0.0/mkmf.rb:340:in `block (2 levels) 
          in postpone'
          from C:/Ruby200-x64/lib/ruby/2.0.0/mkmf.rb:310:in `open'
          from C:/Ruby200-x64/lib/ruby/2.0.0/mkmf.rb:340:in `block in postpone'
          from C:/Ruby200-x64/lib/ruby/2.0.0/mkmf.rb:310:in `open'
          from C:/Ruby200-x64/lib/ruby/2.0.0/mkmf.rb:336:in `postpone'
          from C:/Ruby200-x64/lib/ruby/2.0.0/mkmf.rb:894:in `checking_for'
          from C:/Ruby200-x64/lib/ruby/2.0.0/mkmf.rb:945:in `have_library'
          from extconf.rb:2:in `&lt;main&gt;'
  
  
  Gem files will remain installed in C:/Ruby200-x64/lib/ruby/gems/
  2.0.0/gems/unf_ext-0.0.6 for inspection.
  Results logged to C:/Ruby200-x64/lib/ruby/gems/2.0.0/gems/unf_ext-0.0.6/
  ext/unf_ext/gem_make.out
  </code></pre>