Yelp platform detection of Unity

[Kevin Godby]

Some more information. It looks like the Yelp package on Launchpad
hasn't been updated in quite some time.  The release URL pattern is
now incorrect. It should end with .tar.xz instead of .tar.gz.  The
latest release of Yelp (which includes the patch for Ubuntu/Unity) is
3.9.91.  The current version of Yelp in Saucy is 3.8.1.

Ideas as to what I can do to help facilitate getting Yelp 3.9.31 into Saucy?

—Kevin