Auto install dependencies

Hi Jesper,

Thanks a lot for writing simple-blog.

I was going to make one myself as I could not find anything similar last time I searched, but yesterday I looked up "django simple blog" hoping to find tips, and lo and behold, there's now a package!

I changed a few things relating to requirements to make the installation more seamless. There's still an issue with the simple math library, but I feel the proper solution is to try to fix it on PyPI, so I'll probably give it a shot sometime soon.

Thanks again!

-Ahmed