$ bundle
Fetching gem metadata from https://rubygems.org/
Fetching version metadata from https://rubygems.org/
Fetching dependency metadata from https://rubygems.org/
Resolving dependencies...
Rubygems 2.0.14.1 is not threadsafe, so your gems will be installed one at a time. Upgrade to Rubygems 2.1.0 or higher to enable parallel gem installation.
Using fast-stemmer 1.0.2
Using directory_watcher 1.4.1
Using kramdown 0.13.8
Using liquid 2.4.1
Using syntax 1.0.0
Using posix-spawn 0.3.6
Using yajl-ruby 1.1.0


Your user account isn't allowed to install to the system Rubygems.
  You can cancel this installation and run:

      bundle install --path vendor/bundle

  to install the gems into ./vendor/bundle/, or you can enter your password
  and install the bundled gems to Rubygems using sudo.

  Password:
Installing nokogiri 1.5.9 with native extensions

Gem::Installer::ExtensionBuildError: ERROR: Failed to build gem native extension.

    /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/bin/ruby extconf.rb
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
-----
libxml2 is missing.  please visit http://nokogiri.org/tutorials/installing_nokogiri.html for help with installing dependencies.
-----
*** 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=/System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/bin/ruby
	--with-zlib-dir
	--without-zlib-dir
	--with-zlib-include
	--without-zlib-include=${zlib-dir}/include
	--with-zlib-lib
	--without-zlib-lib=${zlib-dir}/lib
	--with-iconv-dir
	--without-iconv-dir
	--with-iconv-include
	--without-iconv-include=${iconv-dir}/include
	--with-iconv-lib
	--without-iconv-lib=${iconv-dir}/lib
	--with-xml2-dir
	--without-xml2-dir
	--with-xml2-include
	--without-xml2-include=${xml2-dir}/include
	--with-xml2-lib
	--without-xml2-lib=${xml2-dir}/lib
	--with-xslt-dir
	--without-xslt-dir
	--with-xslt-include
	--without-xslt-include=${xslt-dir}/include
	--with-xslt-lib
	--without-xslt-lib=${xslt-dir}/lib
	--with-libxslt-config
	--without-libxslt-config
	--with-pkg-config
	--without-pkg-config
	--with-libxml-2.0-config
	--without-libxml-2.0-config
	--with-libiconv-config
	--without-libiconv-config
	--with-iconvlib
	--without-iconvlib
	--with-xml2lib
	--without-xml2lib


Gem files will remain installed in /var/folders/hd/nfp3wlg90ms2ksf9ttkjymtr0000gn/T/bundler20160821-71083-100pf4enokogiri-1.5.9/gems/nokogiri-1.5.9 for inspection.
Results logged to /var/folders/hd/nfp3wlg90ms2ksf9ttkjymtr0000gn/T/bundler20160821-71083-100pf4enokogiri-1.5.9/gems/nokogiri-1.5.9/ext/nokogiri/gem_make.out
Using sass 3.2.5
Using bundler 1.12.5
Using classifier 1.3.3
Using maruku 0.6.1
Using pygments.rb 0.3.7
An error occurred while installing nokogiri (1.5.9), and Bundler cannot continue.
Make sure that `gem install nokogiri -v '1.5.9'` succeeds before bundling.