Add Ruby 2.6 fixing issues

* Remove existing Tokens#filter (Array#filter) for Ruby 2.6 compatibility.
* Install proper version's rdoc considering installed Ruby version.

1 files changed, 1 insertions, 1 deletions

diff --git a/Gemfile b/Gemfile
index 530c0e8..c19ac08 100644
--- a/Gemfile
+++ b/Gemfile
@@ -14,5 +14,5 @@ group :development do
   gem 'shoulda-context',  RUBY_VERSION < '1.9' ? '= 1.2.1'    : '>= 1.2.1'
   gem 'test-unit',        RUBY_VERSION < '1.9' ? '~> 2.0'     : '>= 3.0'
   gem 'json', '>= 1.8' if RUBY_VERSION < '1.9'
-  gem 'rdoc',             RUBY_VERSION < '1.9' ? '~> 4.2.2'   : '>= 4.2.2'
+  gem 'rdoc',             Gem::Version.new(RUBY_VERSION) < Gem::Version.new('1.9.3') ? '~> 4.2.2' : Gem::Version.new(RUBY_VERSION) < Gem::Version.new('2.2.2') ? '< 6' : '>= 6'
 end