instead of linking to posts only on a user's blog.

Ref T681

changed to use stm.URL for imgs for readability
fixed error in append statement
reordered import statements

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 moves `hostName` to the `Collection` struct, where it's needed. The
field is populated after successful `GetCollection...()` calls.

This isn't the cleanest way to do things, but it accomplishes the goal.
Eventually, we should accept the AppCfg to `GetCollection...()` calls,
or make them `App` methods, instead of `datastore` methods.

Ref T613