Fix install-time gem version incompatibilities

    Gem::RuntimeRequirementNotMetError: public_suffix requires Ruby version >= 1.9.3. The current ruby version is 1.8.
    An error occurred while installing public_suffix (1.4.2), and Bundler cannot continue.

    Gem::RuntimeRequirementNotMetError: redcarpet requires Ruby version >= 1.9.2. The current ruby version is 1.8.
    An error occurred while installing redcarpet (3.1.1), and Bundler cannot continue.

    Gem::RuntimeRequirementNotMetError: rubyzip requires Ruby version >= 1.9.2. The current ruby version is 1.8.
    An error occurred while installing rubyzip (1.0.0), and Bundler cannot continue.

Author: pirj

Gemfile

@@ -11,9 +11,9 @@ gem 'yard', '~> 0.9.24', :require => false
 
 ### deps for rdoc.info
 group :documentation do
-  gem 'redcarpet'
-  gem 'github-markup'
   if RUBY_VERSION > '2.0.0'
+    gem 'redcarpet'
+    gem 'github-markup'
     gem 'relish'
   end
 end
@@ -79,7 +79,7 @@ end
 if RUBY_VERSION <= '1.8.7'
   # cucumber and gherkin require rubyzip as a runtime dependency on 1.8.7
   # Only < 1.0 supports 1.8.7
-  gem 'rubyzip', '<= 1.0'
+  gem 'rubyzip', '< 1.0'
 elsif RUBY_VERSION < '2.4'
   gem 'rubyzip', '>= 1.2.2', '< 2.0.0'
 end

Gemfile-rails-dependencies

@@ -67,7 +67,15 @@ end
 
 gem "nio4r", '< 2.4.0' if RUBY_VERSION < '2.3'
 
-gem "public_suffix", '< 4.0.0' if RUBY_VERSION < '2.3'
+if RUBY_VERSION < '1.9.3'
+  gem "public_suffix", '< 1.4.0'
+elsif RUBY_VERSION < '2.0'
+  gem "public_suffix", '< 2.0.0'
+elsif RUBY_VERSION < '2.1'
+  gem "public_suffix", '< 3.0.0'
+elsif RUBY_VERSION < '2.3'
+  gem "public_suffix", '< 4.0.0'
+end
 
 # rack 2.1.0 introduces a deprecation warning that rails is triggering,
 # but in later versions this warning is removed.