Move coverage-related setup back to spec_helper

These tools must be loaded before our regular Rails environment.

spec/spec_helper.rb

+if ENV['SIMPLECOV']
+  require 'simplecov'
+  SimpleCov.start :rails
+end
+
+if ENV['COVERALLS']
+  require 'coveralls'
+  Coveralls.wear_merged!
+end
+
 ENV["RAILS_ENV"] ||= 'test'
+
 require File.expand_path("../../config/environment", __FILE__)
 require 'rspec/rails'
 require 'shoulda/matchers'

spec/support/coverage.rb

-if ENV['SIMPLECOV']
-  require 'simplecov'
-end
-
-if ENV['COVERALLS']
-  require 'coveralls'
-  Coveralls.wear_merged!
-end