Unable to bundle install (nokogiri 1.5.2) old project, new computer - ruby-on-rails

Question

Having not touched my Rails application for around a year, I decided to try to get the application up and running but am stuck because what I believe to be a dependency somewhere in my Gemfile. I have included it at the bottom.
My issue is that I am running into the error:
ERROR: Error installing nokogiri:
ERROR: Failed to build gem native extension.
/System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/bin/ruby extconf.rb
extconf.rb:10:in `<main>': Use RbConfig instead of obsolete and deprecated Config.
extconf.rb:10:in `<main>': Use RbConfig instead of obsolete and deprecated Config.
extconf.rb:11:in `<main>': Use RbConfig instead of obsolete and deprecated Config.
checking for libxml/parser.h... yes
checking for libxslt/xslt.h... yes
checking for libexslt/exslt.h... yes
checking for iconv_open() in iconv.h... no
checking for iconv_open() in -liconv... yes
checking for xmlParseDoc() in -lxml2... no
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libxml2 is missing. please visit http://nokogiri.org/tutorials/installing_nokogiri.html for help with installing dependencies.
-----
An error occurred while installing nokogiri (1.5.2), and Bundler cannot continue.
Make sure that `gem install nokogiri -v '1.5.2'` succeeds before bundling.
However upon trying to install Nokogiri separately, I found that I am able to install -v 1.6.3.1 without error. I know that libxml2, libiconv, etc., are installed in my computer but am unsure if the versions match with what Nokogiri 1.5.2 is expecting. Also, I tried using the xcode-select --install approach but to no avail.
So my questions are:
How can I update my gemfile to use Nokogiri 1.6.3.1, which I am able to install. When I don't know which gem is using it as a dependecy, is there a way to look that up?
Without removing each gem one by one, is there a way to figure out/remove Nokogiri all together?
If there is no way to do #1 or #2, then how can I successfully install Nokogiri 1.5.2?
Gemfile:
source 'http://rubygems.org'
gem 'rails', '3.2.8'
gem 'faker', '1.0.1'
gem 'will_paginate', '3.0.3'
gem 'sass-rails', '3.2.4'
gem 'coffee-rails', '3.2.2'
gem 'compass-rails'
gem 'compass-960-plugin'
gem 'uglifier', '1.2.3'
gem 'chosen-rails'
gem 'bbcoder'
gem 'sanitize'
gem 'devise'
gem 'possessive'
gem 'err_merchant', :git => "git://github.com/iindigo/err_merchant.git"
gem 'impressionist'
#gem 'kaminari'
#gem 'bcrypt-ruby', '3.0.1' to use rails has_secure_passwordv
group :development do
gem 'sqlite3', '1.3.5'
gem 'annotate', '2.5.0'
gem 'rails-erd'
gem 'rack-mini-profiler'
end
# Gems used only for assets and not required
# in production environments by default.
group :assets do
end
gem 'jquery-rails'
gem 'rails_tokeninput', '1.6.1.rc1'
gem 'selectivizr-rails'
gem 'friendly_id'
gem 'haml'
gem 'browser'
group :test, :development do
gem 'rspec-rails', '2.8.1'
gem 'spork', '0.9.0'
end
group :test do
gem 'capybara', '1.1.2'
gem 'factory_girl_rails', '1.4.0'
end
group :production do
gem 'sqlite3', '1.3.5'
# gem 'therubyracer'
end

Answer 1

sudo apt-get install ruby-dev libxml2-dev libxslt-dev and then try running bundle install again.

Answer 2

I figured out that by doing the command bundle update "gemnamehere" it was possible to get a list of the dependencies of each gem in the case of failure to update.
This in turn allowed me to figure out which gems I needed to change in-order to get Nokogiri to update.