Merge pull request #349 from rspec/pin_ffi

Pin ffi on  1.8.7

Author: JonRowe

Gemfile

@@ -22,6 +22,8 @@ end
 
 if RUBY_VERSION < '2.0.0' && !!(RbConfig::CONFIG['host_os'] =~ /cygwin|mswin|mingw|bccwin|wince|emx/)
   gem 'ffi', '< 1.9.15' # allow ffi to be installed on older rubies on windows
+elsif RUBY_VERSION < '1.9'
+  gem 'ffi', '< 1.9.19' # ffi dropped Ruby 1.8 support in 1.9.19
 end
 
 # No need to run rubocop on earlier versions