code-coverage: exclude spec and features dir from coverage analysis

by default, the whole project is scanned. Code Climate excludes test directories
 from analysis, we do the same on local machine

[skip ci]

spec/spec_helper.rb

@@ -3,8 +3,12 @@
 require 'docker_registry2'
 
 if ENV['COVERAGE']
+  puts 'Enabling coverage'
   require 'simplecov'
-  SimpleCov.start
+  SimpleCov.start do
+    add_filter "/spec/"
+    add_filter "/features/"
+  end
 end
 
 # This file was generated by the `rspec --init` command. Conventionally, all