#  ~  sudo gem install shenzhen
Password:
Building native extensions.  This could take a while...
ERROR:  Error installing shenzhen:
    ERROR: Failed to build gem native extension.

    /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/bin/ruby -r ./siteconf20150715-80705-c762g.rb extconf.rb
creating Makefile

make "DESTDIR=" clean

make "DESTDIR="
compiling generator.c
In file included from generator.c:1:
In file included from ./../fbuffer/fbuffer.h:5:
In file included from /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.10.sdk/System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/include/ruby-2.0.0/ruby.h:33:
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.10.sdk/System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/include/ruby-2.0.0/ruby/ruby.h:24:10: fatal error: 'ruby/config.h' file not found
#include "ruby/config.h"
         ^
1 error generated.
make: *** [generator.o] Error 1

make failed, exit code 2