Convert Pelias setup tutorial blog post into a documentation page

[orangejulius]

@sevko wrote a great blog post, but it's now out of date. We need to rewrite that blog post in an up to date way, and then change the blog page to a 301 permanent redirect to the documentation, so that no one is reading out of date docs.

[dianashk]

Great catch. Let's do this in conjunction with setting up the new importer plugin ecosystem.

[orangejulius]

I'm realizing now that this is really a tutorial for the vagrant image and is still mostly relevant, but separate from our recently created full, manual installation docs. This blog post should probably still be integrated into the Vagrant readme so that it stays up to date.

[orangejulius]

The blog post now has some headers that redirect people to the installation docs!