Successfully interpret class methods

just about closes #24

test/mains/source/add__4.rb

@@ -1,5 +1,5 @@
 class Space
   def main(arg)
-    return 2 +2
+    return 2 + 2
   end
 end

test/mains/source/simple-class__4.rb

@@ -0,0 +1,8 @@
+class Space
+  def self.simple
+    return 2 + 2
+  end
+  def main(arg)
+    return Space.simple
+  end
+end