Installing wagn to ec2 error+issues

installing on ec2 had the following error:

[ec2-user@ip-172-31-17-125 tmp]$ gem install wagn

Building native extensions.  This could take a while...

ERROR:  Error installing wagn:

ERROR: Failed to build gem native extension.

    /usr/bin/ruby2.0 extconf.rb

mkmf.rb can't find header files for ruby at /usr/share/ruby/include/ruby.h

Gem files will remain installed in /home/ec2-user/.gem/ruby/2.0/gems/rmagick-2.13.4 for inspection.

Results logged to /home/ec2-user/.gem/ruby/2.0/gems/rmagick-2.13.4/ext/RMagick/gem_make.out