Add file name in the output of script/runner

Hi,

when you run some script with script/runner and some kind of error
happens the output is something like this:

--- test.rb ---
raise 'bad bad bad'
--- eof ---

$ script/runner lib/test.rb
/Library/Ruby/Gems/1.8/gems/rails-2.1.0/lib/commands/runner.rb:45:
(eval):2: bad bad bad (RuntimeError)
  from /Library/Ruby/Site/1.8/rubygems/custom_require.rb:27:in `eval'
  from /Library/Ruby/Gems/1.8/gems/rails-2.1.0/lib/commands/runner.rb:
45
  from /Library/Ruby/Site/1.8/rubygems/custom_require.rb:27:in
`gem_original_require'
  from /Library/Ruby/Site/1.8/rubygems/custom_require.rb:27:in
`require'
  from script/runner:3

This little patch <http://rails.lighthouseapp.com/projects/8994/
tickets/752-add-file-name-in-script-runner> change this behaviour to
work like this:

$ script/runner lib/test.rb
lib/test.rb:1: bad bad bad (RuntimeError)
  from /Library/Ruby/Site/1.8/rubygems/custom_require.rb:27:in `eval'
  from /Users/daniel/programacion/cosas-rails/test_app_2_1_0/vendor/
rails/railties/lib/commands/runner.rb:45
  from /Library/Ruby/Site/1.8/rubygems/custom_require.rb:27:in
`gem_original_require'
  from /Library/Ruby/Site/1.8/rubygems/custom_require.rb:27:in
`require'
  from script/runner:3

Which is a little more useful (specially the line information).

It's only a one line enhancement. Do somebody have any feedback?

Thanks.