Implement inreplace natively in Ruby

I found yet another instance where the escaping wasn't perfect, so got fed up and just did it in Ruby. I hope this works for all existing usage. It should.

The bonus here is that you can use RegExps now.

Library/Homebrew/utils.rb

@@ -149,13 +149,8 @@ end
 
 # replaces before with after for the file path
 def inreplace path, before, after
-  before=Regexp.escape before.to_s
+  f = File.open(path, 'r')
-  before.gsub! "/", "\\/" # I guess not escaped as delimiter varies
+  o = f.read.gsub(before, after)
-  after=after.to_s
+  f.reopen(path, 'w').write(o)
-  after.gsub! "\\", "\\\\"
+  f.close
-  after.gsub! "/", "\\/"
-  after.gsub! "$", "\\$"
-
-  # FIXME use proper Ruby for teh exceptions!
-  safe_system "/usr/bin/perl", "-pi", "-e", "s/#{before}/#{after}/g", path
 end