title: gem pg not installing
body: <p>So I had to reinitialize a project after my pc crashed and am in the process of reinstalling all my gems on ruby.  Unfortunately when I run bundle install I get the following error.</p>
  
  <pre><code>Building native extensions.  This could take a while...
  ERROR:  Error installing pg:
      ERROR: Failed to build gem native extension.
  
  current directory: /usr/lib/ruby/gems/2.3.0/gems/pg-0.21.0/ext
  /usr/bin/ruby2.3 -r ./siteconf20170925-462-dsymf.rb extconf.rb
  mkmf.rb can't find header files for ruby at /usr/lib/ruby/include/ruby.h
  
  extconf failed, exit code 1
  
  Gem files will remain installed in /usr/lib/ruby/gems/2.3.0/gems/pg-0.21.0 
  for inspection.
  Results logged to /usr/lib/ruby/gems/2.3.0/extensions/x86_64-linux/2.3.0/pg-
  0.21.0/gem_make.out
  </code></pre>
  
  <p>If someone could give me a point in the right direction it would be greatly appreciated.</p>