Add autowrapt instructions for Django 1.9

Author: pglombardo

README.md

@@ -24,10 +24,14 @@ For this BETA, we currently support tracing of Django and Flask applications or
 
 ## Django
 
-To enable the Django instrumentation, set the following environment variable in your _application boot environment_ and then restart your application:
+For Django versions >= 1.10 set the following environment variable in your _application boot environment_ and then restart your application:
 
   `export AUTOWRAPT_BOOTSTRAP=django`
 
+For Django version 1.9.x, instead set:
+
+  `export AUTOWRAPT_BOOTSTRAP=django19`
+
 ## Flask
 
 To enable the Flask instrumentation, set the following environment variable in your _application boot environment_ and then restart your application: