Fix Rails 3.2 compatibility by not using try

The ActiveSupport `try` method works differently in different versions of Rails.
In some versions it checks `respond_to?`; others do not. It is safer (and more
compatible) to explicitly use `respond_to?` instead.

CHANGELOG.md

@@ -11,6 +11,8 @@ lesser changes or bug fixes.
 ## [Unreleased][]
 
 * Your contribution here!
+* Fix a regression in 0.1.20 that broke Rails 3.2 apps
+  [#72](https://github.com/brentd/xray-rails/pull/72)
 
 ## [0.1.20][] (2016-05-18)
 

lib/xray/middleware.rb

@@ -59,7 +59,7 @@ def call(env)
           # Modifying the original response obj maintains compatibility with other middlewares
           if ActionDispatch::Response === response
             response.body = [body]
-            response.header['Content-Length'] = content_length unless response.try(:committed?)
+            response.header['Content-Length'] = content_length unless committed?(response)
             response.to_a
           else
             headers['Content-Length'] = content_length
@@ -73,6 +73,10 @@ def call(env)
 
     private
 
+    def committed?(response)
+      response.respond_to?(:committed?) && response.committed?
+    end
+
     def inject_xray_bar!(html)
       html.sub!(/<body[^>]*>/) { "#{$~}\n#{render_xray_bar}" }
     end