root@2556:~/go-derper-master# gem install memcache
Fetching: memcache-1.2.13.gem (100%)
Building native extensions.  This could take a while...
ERROR:  Error installing memcache:
	ERROR: Failed to build gem native extension.

        /usr/bin/ruby1.9.1 extconf.rb
/usr/lib/ruby/1.9.1/rubygems/custom_require.rb:36:in `require': cannot load such file -- mkmf (LoadError)
	from /usr/lib/ruby/1.9.1/rubygems/custom_require.rb:36:in `require'
	from extconf.rb:4:in `<main>'


Gem files will remain installed in /var/lib/gems/1.9.1/gems/memcache-1.2.13 for inspection.
Results logged to /var/lib/gems/1.9.1/gems/memcache-1.2.13/ext/gem_make.out
root@2556:~/go-derper-master# gem install memcacheex.rb
ERROR:  Could not find a valid gem 'memcacheex.rb' (>= 0) in any repository
ERROR:  Possible alternatives: memcachier, memcached-uv, memcache-auth, memcached, memcache_do