Upgrade to Django 1.5.8

Upgrading to latest playdoh-lib which features Django 1.5.8. We are not
ready for django-browserid v0.10 yet, so I re-add this to vendor-local
on version 0.9.

Add django-browserid 0.9 to vendor-local.
Add django-import-export and friends.
Add django-import-export to admin interface.
Increase the number range for the bug_id field.
Merge pull request #737 from akatsoulas/django-import-export

Django import export
Merge pull request #744 from glogiotatidis/upgrade-django

Upgrade to Django 1.5.8
Install six==1.6.1 for django_browserid v0.9