set up rake file tasks

Author: ignacio-chiazzo

Diff for: Rakefile

@@ -1,6 +1,19 @@
 require "bundler/gem_tasks"
 require "rspec/core/rake_task"
+require "rubocop/rake_task"
 
 RSpec::Core::RakeTask.new(:spec)
 
-task default: :spec
+task :default do
+  Rake::Task["test"].invoke
+  Rake::Task["lint"].invoke
+end
+
+task :test do
+  Rake::Task["spec"].invoke
+end
+
+task :lint do
+  RuboCop::RakeTask.new(:rubocop)
+  Rake::Task["rubocop"].invoke
+end