Add drop<=
Handle case of 0 blog posts. Fixes issue #52.
Fix commit 0c52c125: Use `directory-exists?` not `file-exists?`.
Merge branch 'master' of github.com:greghendershott/frog

* 'master' of github.com:greghendershott/frog:
  Add `--ns` commaand line flag. This works just like `-n`, but it creates a .scrbl file, instead.
A few small revisions to commit 191301e0

- Don't use Markdown italic style in the Scribble post template.

- Tweak some command line flags to fit my admittedly subjective
  preference.