Use the plaintext formatting of the Artistic License 2.0

Another case where the license was copied from HTML, but had a nicely
formatted plaintext version (this is the last one, I promise).

This time the source was taken from
<http://www.perlfoundation.org/attachment/legal/artistic-2_0.txt>
Add fields for year and fullname

See
https://github.com/github/choosealicense.com/pull/103#issuecomment-26914863
Merge pull request #103 from IQAndreas/fix-artistic-license-formatting

Use the plaintext formatting of the Artistic License 2.0