Basic support for tables.

Tables allow you to manage the data more efficiently by defining steps
like:

        Given I have a address card
            | Name     | Hans            |
            | Lastname | Dampf           |
            | Street   | In allen Gassen |
            | ZIP      | 4242            |
            | City     | Buxdehude       |

        Given I have a address table
            | Name   | Lastname | Street          | ZIP  | City        |
            | Hans   | Dampf    | In allen Gassen | 4242 | Buxdehude   |
            | Donald | Duck     | I don't know    | 1234 | Entenhausen |

See testfiles/features/005-tables.feature and testfile/radish/steps.py
for usage.