Rails 2.3.8 fix for #preprocess method

Change .gusb! to gsub otherwise a SafeBuffer occurs in Rails 2..3.8

This Might be a relevant fix for Rails 3.2:
https://github.com/rails/rails/commit/594603b45f1248380068c4a32ac62283fe061e82#activesupport/lib/active_support/core_ext/string/output_safety.rb