Fix SimpleCov load order to track all application code

Move SimpleCov.start before any application requires so coverage
tracking captures all loaded files.

Author: cfis

test/abstract_test.rb

@@ -1,9 +1,4 @@
 require 'bundler/setup'
-require 'fileutils'
-require 'minitest/autorun'
-Minitest.load_plugins
-
-require 'ruby-bindgen/config'
 
 if ENV['COVERAGE']
   require 'simplecov'
@@ -17,6 +12,12 @@
   end
 end
 
+require 'fileutils'
+require 'minitest/autorun'
+Minitest.load_plugins
+
+require 'ruby-bindgen/config'
+
 # Set up libclang path from config
 %w[cpp c c/clang-c].each do |dir|
   config = RubyBindgen::Config.new(File.join(__dir__, 'headers', dir, 'bindings.yaml'))