fix <attachment> markup in events section

README.md

@@ -168,10 +168,10 @@ Events
 
 
 Before and after the Post Processing step, Paperclip calls back to the model
 Before and after the Post Processing step, Paperclip calls back to the model
 with a few callbacks, allowing the model to change or cancel the processing
 with a few callbacks, allowing the model to change or cancel the processing
-step. The callbacks are "before_post_process" and "after_post_process" (which
+step. The callbacks are `before_post_process` and `after_post_process` (which
 are called before and after the processing of each attachment), and the
 are called before and after the processing of each attachment), and the
-attachment-specific "before_<attachment>_post_process" and
-"after_<attachment>_post_process". The callbacks are intended to be as close to
+attachment-specific `before_<attachment>_post_process` and
+`after_<attachment>_post_process`. The callbacks are intended to be as close to
 normal ActiveRecord callbacks as possible, so if you return false (specifically
 normal ActiveRecord callbacks as possible, so if you return false (specifically
 - returning nil is not the same) in a before_ filter, the post processing step
 - returning nil is not the same) in a before_ filter, the post processing step
 will halt. Returning false in an after_ filter will not halt anything, but you
 will halt. Returning false in an after_ filter will not halt anything, but you