added user test, basic user methods

config/initializers/memcache.rb

@@ -0,0 +1,6 @@
+require 'memcache'
+
+unless defined?(MEMCACHE)
+  MEMCACHE = MemCache.new :c_threshold => 10_000, :compression => true, :debug => false, :namespace => Danbooru.config.app_name.gsub(/[^A-Za-z0-9]/, "_"), :readonly => false, :urlencode => false
+  MEMCACHE.servers = Danbooru.config.memcached_servers
+end