Also ensure newline at EOF.

This was achieved by running the new normalize_coop_frontmatter.rb
script which basically reads in the frontmatter, parses it and dumps it
back out.

I had to manually fix some telephone numbers which had been incorrectly
parsed as some kind of number rather than as strings.

I've populated the data, where available, from the field "Number of
current members The number of full members (owners) in the co-op." in
the wordpress admin.

I ran `ruby migrate_coop_pages.rb` in `scripts`. There will need to be
some manual tidying up of the generated `.md` files under `_coops` but
I think this is a good start. As a one-off it doesn't warrant the time
it would take to improve the migration script.