Chore: Setup test coverage in codeclimate [#332] (#333)

Gemfile.lock

@@ -136,6 +136,7 @@ GEM
       devise (> 3.5.2, < 5)
       rails (>= 4.2.0, < 6.1)
     diff-lcs (1.3)
+    docile (1.3.2)
     domain_name (0.5.20190701)
       unf (>= 0.0.5, < 1.0.0)
     dotenv (2.7.5)
@@ -361,6 +362,11 @@ GEM
       rack-protection (>= 2.0.0)
       redis (>= 4.1.0)
     simple_oauth (0.3.1)
+    simplecov (0.17.1)
+      docile (~> 1.1)
+      json (>= 1.8, < 3)
+      simplecov-html (~> 0.10.0)
+    simplecov-html (0.10.2)
     spring (2.1.0)
     spring-watcher-listen (2.0.1)
       listen (>= 2.7, < 4.0)
@@ -481,6 +487,7 @@ DEPENDENCIES
   sentry-raven
   shoulda-matchers
   sidekiq
+  simplecov
   spring
   spring-watcher-listen
   telegram-bot-ruby