Add configuration instructions for RSpec timeout

README.md

@@ -48,6 +48,22 @@ mutant --include lib --require virtus --use rspec Virtus::Attribute.build
 mutant --include lib --require virtus --use rspec Virtus::Attribute#type
 ```
 
+Configuration
+-------------
+
+Occasionally mutant will produce a mutation with an infinite runtime. When this happens
+mutant will look like it is running indefinitely without killing a remaining mutation. To
+avoid mutations like this, consider adding a timeout around your tests. For example, in
+RSpec you can add the following to your `spec_helper`:
+
+```ruby
+config.around(:each) do |example|
+  Timeout.timeout(5_000, &example)
+end
+```
+
+which will fail specs which run for longer than 5 seconds.
+
 Rails
 -------