this adds basic support for importing files as blog posts.
.txt and .md are supported at this time and the
collection is selectable, defaulting to draft.
if a collection is specified the post is federated.
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
