title: tried installing pg gem and it failed
body: <pre><code>$ gem install pg
  Building native extensions.  This could take a while...
  ERROR:  Error installing pg:
  ERROR: Failed to build gem native extension.
  
  /Users/jtorkornoo/.rbenv/versions/2.1.2/bin/ruby extconf.rb`
  
  
           checking for pg_config... no
  No pg_config... trying anyway. If building fails, please try again with``
      --with-pg-config=/path/to/pg_config 
        checking for libpq-fe.h... no
  Can't find the 'libpq-fe.h header
  *** 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=/Users/jtorkornoo/.rbenv/versions/2.1.2/bin/ruby
      --with-pg
      --without-pg
      --with-pg-config
      --without-pg-config
      --with-pg_config
      --without-pg_config
      --with-pg-dir
      --without-pg-dir
      --with-pg-include
      --without-pg-include=${pg-dir}/include
      --with-pg-lib
      --without-pg-lib=${pg-dir}/lib
  
  extconf failed, exit code 1
  
  Gem files will remain installed in /Users/jtorkornoo/.rbenv/versions/2.1.2/lib/ruby/gems/2.1.0/gems/pg-0.17.1 for inspection.
  Results logged to /Users/jtorkornoo/.rbenv/versions/2.1.2/lib/ruby/gems/2.1.0/extensions/x86_64-darwin-14/2.1.0-static/pg-0.17.1/gem_make.out
  </code></pre>
  
  <pre>
  
  gem file
  source 'https://rubygems.org'
  
  gem 'rails', '3.2.19'
  
  # Bundle edge Rails instead:
  # gem 'rails', :git => 'git://github.com/rails/rails.git'
  group :development, :test do
    gem 'pg'
  end
  
  
  
  
  
  
  # Gems used only for assets and not required
  # in production environments by default.
  group :assets do
    gem 'sass-rails',   '~> 3.2.3'
    gem 'coffee-rails', '~> 3.2.1'
  
    # See https://github.com/sstephenson/execjs#readme for more supported runtimes
    # gem 'therubyracer', :platforms => :ruby
  
    gem 'uglifier', '>= 1.0.3'
  end
  
  gem 'jquery-rails'
  
  # To use ActiveModel has_secure_password
  # gem 'bcrypt-ruby', '~> 3.0.0'
  
  # To use Jbuilder templates for JSON
  # gem 'jbuilder'
  
  # Use unicorn as the app server
  # gem 'unicorn'
  
  # Deploy with Capistrano
  # gem 'capistrano'
  
  # To use debugger
  # gem 'debugger'
  
  </pre>