[xmlunit/xmlunit.net] 553f65: try installing the latest nuget on appveyor

[GitHub <no...@gi...>]

  Branch: refs/heads/master
  Home:   https://github.com/xmlunit/xmlunit.net
  Commit: 553f65b0fce307b9fcafbd1029f5a6f2496299c3
      https://github.com/xmlunit/xmlunit.net/commit/553f65b0fce307b9fcafbd1029f5a6f2496299c3
  Author: Stefan Bodewig <ste...@fr...>
  Date:   2015-12-11 (Fri, 11 Dec 2015)

  Changed paths:
    M appveyor.yml

  Log Message:
  -----------
  try installing the latest nuget on appveyor