Change Mom to SlotMachine

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

lib/slot_machine/macro/get_internal_word.rb

@@ -0,0 +1,13 @@
+module Mom
+  class GetInternalWord < Macro
+    def to_risc(compiler)
+      compiler.builder(compiler.source).build do
+        object! << message[:receiver]
+        integer! << message[:arg1] #"at" is at index 0
+        integer.reduce_int
+        object << object[integer]
+        message[:return_value] << object
+      end
+    end
+  end
+end