Updated p5-libwww to 6.22.

6.22      2017-03-01
    - Update Travis-CI to test on minimum versions of prereqs. (GH PR #109)
    - Fix tests that depended on a newer version of HTTP::Message (GH PR #119)
    - Update documentation to reflect behavior difference in ->put() depending
      on the version of HTTP::Message installed. (GH PR #120)

(wiz)