fix pre 2.2. deps

Gemfile

@@ -2,7 +2,13 @@ source 'https://rubygems.org'
 gemspec
 
 group :development do
-  gem 'test-unit' if RUBY_VERSION.start_with?('2.2')
+
+  if RUBY_VERSION.start_with?('2.2')
+    gem 'test-unit'
+  else
+    gem 'minitest', '< 5.0'
+  end
+
   gem 'rake'
   gem 'redgreen', '~> 1.2'
   gem 'shoulda', '~> 3.5'

features/sorting.feature

@@ -191,7 +191,7 @@ Feature: Sorting BibTeX Bibliographies
     Then "Ruby Programming" should come before "Smalltalk" in "_site/scholar.html"
     And I should not see "<i>Ruby Not Cited</i>" in "_site/scholar.html"
 
-  @tags @sorting @wip
+  @tags @sorting
   Scenario: Sort By Year And Month
     Given I have a scholar configuration with:
       | key     | value       |