updated django rest framework to 2.1.15
Fixed compatibility with the 'url' tag from Django 1.5

This works for Django 1.3 and up.
added meta_description field to fiber Page model, added migration

fixed some weird migration bug on Page model 'is_public' field, migration 0010 adds 'is_public' field, migration 0011 had none 'is_public' field
added Page 'meta_description' field to django admin
added meta_description to Fiber front-end admin
Merge pull request #148 from nvandijk/feature/page-meta-description

Page meta description
Added new method to Page model

Check if a Fiber page has visbile children (show_in_menu field must be True). Very useful for templating Fiber page menus.
Merge pull request #151 from nvandijk/dev

Added new method to Page model
Fixed a bug for removing files for Image and File model. Use storage delete mehtod instead of python os file remove. Now it's also working with different file storages backends.
Updated Django Fiber requirements

Pillow to 1.7.8
Django MPTT to 0.5.5
Django compressor to 1.2
Django restframework to 2.1.17
Updated readme
Merge branch 'dev'