this borrows some code from github.com/gogs/gogs/pkg/tool to avoid
pulling it in as a dependency, along with many other indirect deps.

This upgrades the library to v2, which lets you specify that GOMAXPROCs
should always be the max number of CPUs -- and then sets it to that.

One side effect of this is that images are no longer listed in sitemaps.
I'm somehow at a loss on how to build and append the images array we
need, with the library's latest changes.

Fixes #86

This adds https://github.com/jteeuwen/go-bindata as a module dependency
as the make target 'build' will result in it's addition.

This indicates whether or not invites are enabled on this instance. It
requires an upgrade to writefreely/go-nodeinfo v1.2.0