Revert "Runtime metrics are now automatic. Remove runtime section."

This reverts commit f7a16d4.

Author: pglombardo

README.md

@@ -35,6 +35,14 @@ To enable the Flask instrumentation, set the following environment variable in y
 
   `export AUTOWRAPT_BOOTSTRAP=flask`
 
+## Runtime Monitoring Only
+
+_Note: When the Django or Flask instrumentation is used, runtime monitoring is automatically included.  Use this section if you only want to see runtime metrics._
+
+To enable runtime monitoring (without request tracing), set the following environment variable in your _application boot environment_ and then restart your application:
+
+  `export AUTOWRAPT_BOOTSTRAP=runtime`
+
 ## uWSGI
 
 ### Threads