Add Simplecov for coverage

Not very impressive at the moment because Shindo is not wired up but it
all helps.

fog.gemspec

@@ -80,6 +80,7 @@ Gem::Specification.new do |s|
   s.add_development_dependency("rbvmomi")
   s.add_development_dependency("rubocop") if RUBY_VERSION > "1.9"
   s.add_development_dependency("shindo", "~> 0.3.4")
+  s.add_development_dependency("simplecov")
   s.add_development_dependency("thor")
   s.add_development_dependency("yard")
 

spec/spec_helper.rb

@@ -1,3 +1,11 @@
+if ENV["COVERAGE"]
+  require "simplecov"
+
+  SimpleCov.start do
+    add_filter "/spec/"
+  end
+end
+
 require "minitest/autorun"
 require "minitest/spec"
 require "minitest/stub_const"