* zola init works without argument (defaults to current directory)
* zola init works with existing folders (no non-hidden files permitted)
* Update zola init documentation
* [docs] Optional argument is on a separate line for clarity
* Add tests for init subcommand's respect of existing folders
* Add check subcommand
* Add some brief documentation for the check subcommand
* Start working on parallel link checks
* Check all external links in Site
* Return *all* dead links in site
Separate interface and base_url for serve
You can now have a different base_url and listening interface.
The `gutenberg serve` cmd now accepts `-u`/`--base-url`, but it defaults to `127.0.0.1`.
