changed valid? method to check also correctness of isbn13

[jbutton]

I've renamed current valid? method to valid_checksum?
in new valid? method i'm using parts method to find if ISBN is valid.

But I'm not sure if parts method check is needed for ISBN10 since it is valid when checksum is correct.
So perhaps:

 def valid_isbn_10?
    valid_checksum_isbn_10? #would be better
    # instead of !parts(4).blank?
  end

  def valid_isbn_13?
    !parts.blank?
  end

[jbutton]

Ok
First thing to correct: forgot to cache new methods. I'll add it to cache_method with feedback.

[ragalie]

Should this use valid??

[jbutton]

Yeap, it's now doing proper isbn10 validation.

[ragalie]

LGTM, thanks! If these changes are ready to go fix the conflicts and let us know and we'll get them merged in.