Add option to separate categories from tags
Output lowercase file names, to match middleman-blog conventions.
Check for nil tags
Tags now contain BOTH tags and categories. There is now the option of appending categories as a separate property, but "tag" will always contain both WP tag and category
Make convert to html its own setting, and only perform the action if there is HTML inside the post.
Create Gemfile, and update readme.md with requirements list.
Rename setting, hoping it will be clearer
Categories are now fully separate YAML property from tags.
When converting from HTML to markdown, preserve double newlines and add newline before HTML tags (such as headers, etc) so markdown generation is more optimal.
Update readme.md
Merge pull request #4 from cyanos/master

Separate categories from tags, improve html->md conversion, add Gemfile, filenames lowercase