Revert to capistrano 3.1. Version 3.2.0 is too buggy.

Most notably the `before` DSL is completely broken in 3.2.0:
https://github.com/capistrano/capistrano/issues/1004
Fix cap requires per capistrano-fiftyfive README
Use correct GH url and syntax (no ssh://)
Merge branch 'master' into bootstrap