Updated to Ruby 3.0.0

Includes temporary disablement of gem dependencies that require
updating to Ruby 3.0.0 first.

[Details](https://chl.li/LdWrE).

.ruby-version

@@ -1 +1 @@
-2.7.2
+3.0.0

Gemfile

@@ -3,4 +3,4 @@
 source "https://rubygems.org"
 
 gem "rake", "~> 13.0"
-gem "git-lint", "~> 1.3"
+# gem "git-lint", "~> 1.4"

Rakefile

@@ -1,5 +1,5 @@
 # frozen_string_literal: true
 
-require "git/lint/rake/setup"
+# require "git/lint/rake/setup"
 
-task default: :git_lint
+# task default: :git_lint

circle.yml

@@ -24,9 +24,9 @@ jobs:
       - run:
           name: Ruby Install
           command: |
-            curl https://cache.ruby-lang.org/pub/ruby/${CI_RUBY_VERSION::-2}/ruby-$CI_RUBY_VERSION.tar.bz2 > ../ruby-$CI_RUBY_VERSION.tar.gz
             cd ..
-            tar --extract --bzip2 --verbose --file ruby-$CI_RUBY_VERSION.tar.gz
+            curl https://cache.ruby-lang.org/pub/ruby/${CI_RUBY_VERSION::-2}/ruby-$CI_RUBY_VERSION.tar.gz > ruby-$CI_RUBY_VERSION.tar.gz
+            tar --extract --gzip --verbose --file ruby-$CI_RUBY_VERSION.tar.gz
             cd ruby-$CI_RUBY_VERSION
             ./configure
             make