Make SyntaxError display the message when printed

This seems to be the way to make ruby errors look best. I tested it like this:

```ruby
$ cat /tmp/a.rb
class A < StandardError
  def initialize(a)
    @A = a
  end
end

class B < StandardError
  attr_reader :message
  def initialize(message)
    @message = message
  end
end

class C < StandardError
  def initialize(message)
    super(message)
  end
end

puts A.new('foo')
puts A.new('foo').inspect
puts A.new('foo').message
puts B.new('foo')
puts B.new('foo').inspect
puts B.new('foo').message
puts C.new('foo')
puts C.new('foo').inspect
puts C.new('foo').message
$ ruby /tmp/a.rb
A
#<A: A>
A
B
#<B: B>
foo
foo
#<C: foo>
foo
```

Author: ptarjan

lib/message_format/parser.rb

@@ -360,15 +360,14 @@ def self.parse ( pattern )
     #
     class SyntaxError < StandardError
 
-      attr_reader :message
       attr_reader :expected
       attr_reader :found
       attr_reader :offset
       attr_reader :line
       attr_reader :column
 
       def initialize (message, expected, found, offset, line, column)
-        @message = message
+        super(message)
         @expected = expected
         @found = found
         @offset = offset