leave assignee as name_expression in assignment, fix tests accordingly

lib/ast/basic_expressions.rb

@@ -29,7 +29,7 @@ module Ast
       variable
     end
     def inspect
-      self.class.name + ".new(" + name + ")"
+      self.class.name + '.new("' + name + '")'
     end
     def attributes
       [:name]

lib/ast/operator_expressions.rb

@@ -31,7 +31,7 @@ module Ast
       @assignee, @assigned = assignee, assigned
     end
     def inspect
-      self.class.name + ".new(" + assignee + ", " + assigned.inspect+ ")"
+      self.class.name + ".new(" + assignee.inspect + ", " + assigned.inspect + ")"
     end
     
     def compile context