depend on ruby 2.2.6
depend on ruby 2.2.6

That's the requirement for rbnacl 5.0
ruby 2.1 is EOL since 2017-03-31 anyways

Signed-off-by: Marc-Antoine Perennou <07f76cf0511c79b361712839686f3cee8c75791c@Perennou.com>

localmed/ruby-macaroons