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.

GetCollections and GetPublishableCollections now take a hostname
parameter to allow setting the collecion hostname.

All collections used in memory now have their hostname set.

this changes GetPinnedPosts to accept an includeFutre bool, which
returns future dated pinned posts when true.

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