Deal with new ffi Ruby version requirement

CI was failing for 1.9.2 and 1.9.3. This is due to
ffi/ffi#683

Related:
- ffi/ffi#699

Gemfile

@@ -22,8 +22,10 @@ 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
+elsif RUBY_VERSION < '2.0'
+  # ffi dropped Ruby 1.8 support in 1.9.19
+  # ffi dropped Ruby 1.9 support in 1.11.0
+  gem 'ffi', '< 1.9.19'
 else
   gem 'ffi', '~> 1.9.25'
 end