1. Replaced category IDs with (string) category names: the extra level of indirection wasn't buying anyone anything.
2. Modified the preprocessor accordingly.
3. Wrote bin/categories.py to list categories and blog posts.
Now that blog posts use the names of people and categories directly,
we don't need the indirection tables in standard_config.yml, so they
have been deleted.
Updating documentation on writing blog posts
Merge pull request #18 from gvwilson/using-names-instead-of-category-ids

dUsing names instead of category ids