Change method name to avoid conflict in ruby 1.9

lib/spawn.rb

@@ -73,7 +73,7 @@ def self.kill_punks
   # By default the process will be a forked process.   To use threading, pass
   # :method => :thread or override the default behavior in the environment by setting
   # 'Spawn::method :thread'.
-  def spawn(opts = {})
+  def spawn_block(opts = {})
     options = @@default_options.merge(opts.symbolize_keys)
     # setting options[:method] will override configured value in default_options[:method]
     if options[:method] == :yield