Support alternate test-paths with non-flag args

Previously, command lines like `lein spec --tag unit` would use the
default spec location (`specs`), instead of the leiningen `:test-paths`.
The decision of how to parse out the file locations needed to be pushed
down into the cli/mmargs logic, so this adds a new option (inteneded for
internal use only) to provide default spec locations that supercede the
one in `speclj.config/default-config`.

closes #101
Avoid `load-file` for versioning

closes #87