Log Message:
Updated package to latest version, 2.2.0. Changes include:

v2.2.0 (2017-06-20)

    Switch to jbuilder (#13, @rgrinberg)

v2.1.2 (2016-10-18)

    Fix version number (#11, @hannesm)

v2.1.1 (2016-10-03)

    Switch build to topkg and obey the odig conventions for installing
    metadata files.
    Add a test suite based on RFC4648 test vectors.
    Improve Travis CI tests to be multidistro.