Configure SimpleCov properly

* Update the requirement to latest version
* Make sure we actually *check* code coverage. Previously, we were only checking
  files in `spec/`, but not we also check `lib/`

Gemfile

@@ -5,6 +5,7 @@ gem 'rake', '~> 10.0'
 gem 'gist'
 gem 'yard'
 gem 'rspec', '~> 3.8.0'
+gem 'simplecov', '~> 0.16', require: false
 
 # Rubocop supports only >=2.2.0
 if Gem::Version.new(RUBY_VERSION) >= Gem::Version.new('2.2.0')

spec/spec_helper.rb

@@ -1,5 +1,11 @@
-require 'bundler/setup'
-Bundler.require :default, :test
+if ENV['COVERAGE']
+  require 'simplecov'
+  SimpleCov.start
+end
+
+require 'pry'
+require 'rspec'
+
 require 'pry/testable'
 require 'English'
 
@@ -7,11 +13,6 @@ Dir['./spec/support/**/*.rb'].map do |file|
   require file
 end
 
-if ENV["COVERAGE"]
-  require "simplecov"
-  SimpleCov.start
-end
-
 class Module
   # False positive: https://github.com/rubocop-hq/rubocop/issues/5953
   # rubocop:disable Style/AccessModifierDeclarations