Squashed commit of the following:

commit 951be045be7286ce35160f36562b795b2bec7f96
Merge: 1ca9538 47f3482
Author: Gavin Simpson <ucfagls@gmail.com>
Date:   Tue Sep 30 10:22:12 2014 -0600

    Merge pull request #49 from gavinsimpson/master

    fix a bug in calculation of p value in group pairwise permutation test

commit 47f348283bff6c9d8939b2780b62fcde15e1ed84
Author: Gavin Simpson <ucfagls@gmail.com>
Date:   Tue Sep 30 10:01:53 2014 -0600

    fix a bug in calculation of p value in group pairwise permutation test introduced in c6b76f1

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/vegan@2890 edb9625f-4e0d-4859-8d74-9fd3b1da38cb