Rails install on XUbuntu 14.04 (ERROR: Failed to build gem native extension)

I am following the steps on this page verbatim but came across an error when I got to the point of installing Rails.  This is the error I got...

Fetching: nokogiri-1.6.7.1.gem (100%)
Building native extensions.  This could take a while...
ERROR:  Error installing rails:
 ERROR: Failed to build gem native extension.

    /home/user/.rvm/rubies/ruby-2.2.4/bin/ruby -r ./siteconf20151223-26597-j3i7to.rb extconf.rb
checking if the C compiler accepts ... *** 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=/home/user/.rvm/rubies/ruby-2.2.4/bin/$(RUBY_BASE_NAME)
 --help
 --clean
/home/user/.rvm/rubies/ruby-2.2.4/lib/ruby/2.2.0/mkmf.rb:456:in `try_do': The compiler failed to generate an executable file. (RuntimeError)
You have to install development tools first.
 from /home/user/.rvm/rubies/ruby-2.2.4/lib/ruby/2.2.0/mkmf.rb:571:in `block in try_compile'
 from /home/user/.rvm/rubies/ruby-2.2.4/lib/ruby/2.2.0/mkmf.rb:522:in `with_werror'
 from /home/user/.rvm/rubies/ruby-2.2.4/lib/ruby/2.2.0/mkmf.rb:571:in `try_compile'
 from extconf.rb:80:in `nokogiri_try_compile'
 from extconf.rb:87:in `block in add_cflags'
 from /home/user/.rvm/rubies/ruby-2.2.4/lib/ruby/2.2.0/mkmf.rb:619:in `with_cflags'
 from extconf.rb:86:in `add_cflags'
 from extconf.rb:336:in `<main>'

extconf failed, exit code 1

Gem files will remain installed in /home/user/.rvm/gems/ruby-2.2.4/gems/nokogiri-1.6.7.1 for inspection.
Results logged to /home/user/.rvm/gems/ruby-2.2.4/extensions/x86_64-linux/2.2.0/nokogiri-1.6.7.1/gem_make.out

I read many forum posts where I tried a handful of suggestions and none of them worked. I finally came across a stack overflow post where the suggestion of running this command was towards the bottom...

sudo apt-get install libgmp-dev

...or...

sudo apt-get install libgmp3-dev

Many of the suggestions I found on a few different forum posts stated that I needed to run...

sudo apt-get install git-core curl zlib1g-dev build-essential libssl-dev libreadline-dev libyaml-dev libsqlite3-dev sqlite3 libxml2-dev libxslt1-dev libcurl4-openssl-dev python-software-properties libffi-dev

...but given the setup guide I'm following (along with a few notes I've take), I'd already installed all of those packages.  The extra package needs to be installed for XUbuntu 14.04 and the regular Ubuntu 14.04 images in order to install Rails.