Report test coverage to CodeClimate

Coverage gets generated on every build, but we only need to send it for
one build. Send it on the first one, otherwise we get eg:

    ./cc-test-reporter after-build --exit-code $TRAVIS_TEST_RESULT
    time="2019-08-22T12:37:01Z" level=warning msg="Conflict when uploading: A test report for commit 6dabaaa6cd7e4c5c51dc538e4fbb7861ca433d8e already exists, skipping upload"

I guess this is because the test reporter assumes that if coverage
exists, then it has been sent?

Config from here:

https://docs.codeclimate.com/docs/travis-ci-test-coverage#section-travis-ci-single-test-suite-non-parallel-builds

.gitignore

@@ -2,6 +2,7 @@
 *.rbc
 .bundle
 .config
+.coverage
 .yardoc
 Gemfile.lock
 InstalledFiles

.travis.yml

@@ -8,6 +8,12 @@ matrix:
         - gem install bundler
       script: bundle exec rake rubocop # ONLY lint once, first
     - rvm: 2.3.5
+      before_script:
+        - curl -L https://codeclimate.com/downloads/test-reporter/test-reporter-latest-linux-amd64 > ./cc-test-reporter
+        - chmod +x ./cc-test-reporter
+        - ./cc-test-reporter before-build
+      after_script:
+        - ./cc-test-reporter after-build --exit-code $TRAVIS_TEST_RESULT
     - rvm: 2.4.6
     - rvm: 2.5.5
     - rvm: 2.6.3

pundit.gemspec

@@ -27,5 +27,6 @@ Gem::Specification.new do |gem|
   gem.add_development_dependency "rake"
   gem.add_development_dependency "rspec", ">= 3.0.0"
   gem.add_development_dependency "rubocop", "0.74.0"
+  gem.add_development_dependency "simplecov", ">= 0.17.0"
   gem.add_development_dependency "yard"
 end

spec/spec_helper.rb

@@ -1,5 +1,10 @@
 # frozen_string_literal: true
 
+require "simplecov"
+SimpleCov.start do
+  add_filter "/spec/"
+end
+
 require "pundit"
 require "pundit/rspec"