cast name to string

Some times a Pathname is passed in here

Signed-off-by: Adam Vandenberg <flangy@gmail.com>

Library/Homebrew/formula.rb

@@ -347,6 +347,9 @@ class Formula
     # If an instance of Formula is passed, just return it
     return name if name.kind_of? Formula
 
+    # Otherwise, convert to String in case a Pathname comes in
+    name = name.to_s
+
     # If a URL is passed, download to the cache and install
     if name =~ %r[(https?|ftp)://]
       url = name