Clean up SimpleCov usage

.simplecov

@@ -0,0 +1,4 @@
+SimpleCov.start do
+  add_filter "/spec/"
+  add_filter "/tmp/"
+end

features/support/env.rb

@@ -1,7 +1,6 @@
 PROJECT_ROOT = File.expand_path(File.join(File.dirname(__FILE__), '..', '..'))
 
 require "simplecov"
-SimpleCov.start
 
 $: << File.join(PROJECT_ROOT, 'lib')
 

spec/spec_helper.rb

@@ -6,7 +6,6 @@ require 'rspec'
 require 'rspec/autorun'
 
 require "simplecov"
-SimpleCov.start
 
 require 'factory_girl'
 require "mocha"