title: can't install mysql2 using gem
body: <p>I am trying to create a project with mysql as database using rails </p>
  
  <p>I use the following command :</p>
  
  <pre><code> gem install mysql2
  </code></pre>
  
  <p>I get the following result in commandline :</p>
  
  <pre><code>Building native extensions.  This could take a while...
  ERROR:  Error installing mysql2:
      ERROR: Failed to build gem native extension.
  
      /home/sample/.rbenv/versions/2.2.3/bin/ruby -r ./siteconf20170316-5426-f6rn3k.rb extconf.rb
  checking for rb_absint_size()... yes
  checking for rb_absint_singlebit_p()... yes
  checking for ruby/thread.h... yes
  checking for rb_thread_call_without_gvl() in ruby/thread.h... yes
  checking for rb_thread_blocking_region()... no
  checking for rb_wait_for_single_fd()... yes
  checking for rb_hash_dup()... yes
  checking for rb_intern3()... yes
  checking for rb_big_cmp()... yes
  checking for mysql_query() in -lmysqlclient... no
  -----
  mysql client is missing. You may need to 'apt-get install libmysqlclient-dev' or 'yum install mysql-devel', and try again.
  -----
  *** 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/sample/.rbenv/versions/2.2.3/bin/$(RUBY_BASE_NAME)
      --with-mysql-dir
      --without-mysql-dir
      --with-mysql-include
      --without-mysql-include=${mysql-dir}/include
      --with-mysql-lib
      --without-mysql-lib=${mysql-dir}/lib
      --with-mysql-config
      --without-mysql-config
      --with-mysql-dir
      --without-mysql-dir
      --with-mysql-include
      --without-mysql-include=${mysql-dir}/include
      --with-mysql-lib
      --without-mysql-lib=${mysql-dir}/lib
      --with-mysqlclientlib
      --without-mysqlclientlib
  
  extconf failed, exit code 1
  
  Gem files will remain installed in /home/sample/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/mysql2-0.4.5 for inspection.
  Results logged to /home/sample/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/extensions/x86_64-linux/2.2.0-static/mysql2-0.4.5/gem_make.out
  </code></pre>
  
  <p>also as it mentions mysql client missing i tries to install the mentioned module but it did not work out.
  can anyone provide a solution for this ?</p>