Merge pull request #41 from tamouse/bugfix/Issue_40_file_name_too_long

Set a limit on the maximum length of a post file_name.
Merge branch 'master' of github.com:pote/planet.rb
Add blog slug value created from blog name
Update README with new blog_slug
Merge pull request #1 from tamouse/feature/add_blog_slug

Feature/add blog slug