adds while statement to vool

lib/vool/while_statement.rb

@@ -1,5 +1,9 @@
 module Vool
   class WhileStatement < Statement
-    attr_accessor :branch_type , :condition , :statements
+    attr_accessor :condition , :statements
+
+    def initialize( condition )
+      @condition = condition
+    end
   end
 end