added validation checks based on unit testing to category model
added validation checks based on unit testing to category model

Signed-off-by: Holloway, Kean Ho <bbd8faa40b0f348214bf4124b281a301299ba6dd@gmail.com>

hollowaykeanho/craigslist,hollowaykeanho/craigslist,hollowaykeanho/craigslist