rake-task to import a folder with a mapping
useful when the filename does not equal the slug
the input-file should contain one file per line, each line
starting with a slug-prefix ("30C3_-_5192") used to find the event
followed by one or more tabs followed by the filenamed, just as with
import_folder.rake
Merge pull request #5 from MaZderMind/import_folder_with_mapping

rake-task to import a folder with a mapping