Add debug output to Rescanner

lib/brakeman/rescanner.rb

@@ -45,6 +45,8 @@ class Brakeman::Rescanner < Brakeman::Scanner
 
     SCAN_ORDER.each do |type|
       paths_by_type[type].each do |path|
+        warn "Rescanning #{path} as #{type}" if tracker.options[:debug]
+
         if rescan_file path, type
           @changes = true
         end