Sanitizing Names for Files

I use database records for file names when generating reports, but some of those have invalid characters. The attachment_fu plugin has the sanitize_filename method, but I wasn't so happy with the output, e.g.,

 >> sanitize_filename("foo & bar") 
=> "foo___bar" 
 >> sanitize_filename("14th @bar") 
=> "14th__bar" 

So I wrote a prettier sanitization helper:

which gives me:
 >> sanitize_for_filename(" foo & bar ") 
=> "foo_and_bar" 
 >> sanitize_for_filename("14th @bar") 
=> "14th_at_bar" 

Much better.