Merge pull request #59 from asmasma21/master

The slides url is not checked when edited
Merge pull request #60 from asmasma21/master

Fixing #55 : When we edit slides, the slide category is set the first one in the liste and not the default one
Merge pull request #62 from asmasma21/master

Clearing the add new slide form
delete/update categories and added forms
Merge branch 'master' of https://github.com/moztn/slides-moztn
fixed #64:Deleting a category will delete all slides in that category
fixed #49:Adding pagination on the admin page for the slides and the categories
category list id must be defferent slides-list