Change Mom to SlotMachine

rather large commit, but essentially a simple rename
Rationale in docs and blogs

lib/arm/instructions/instruction.rb

@@ -13,7 +13,7 @@ module Arm
       @source = source
       @next = nekst
       return unless source
-      raise "Source must be string or Instruction, not #{source.class}" unless source.is_a?(String) or source.is_a?(Mom::Instruction)
+      raise "Source must be string or Instruction, not #{source.class}" unless source.is_a?(String) or source.is_a?(SlotMachine::Instruction)
     end
     attr_reader :source