Basic blog structure (fix #3)

Ref: #3.

This also intruce swebtest.
This also adds TimestampedModel in ideasbox models.
I'm pretty sure it's bad practice to use those `auto_now*` things. There's a way around that though:
- `auto_now`: modify it in the `save` method
- `auto_now_add`: use a default value of `datetime.datetime.now` (no parens!)