log file is a tempfile

- not sure if there's a need for log file in predefined location
- installer is verbose enough to signal errors

autoload/vundle/scripts.vim

@@ -24,7 +24,7 @@ endf
 
 func! s:view_log()
   if !exists('g:vundle_log_file')
-    let g:vundle_log_file = expand('$HOME/.vim-vundle/vundle.log') 
+    let g:vundle_log_file = tempname()
   endif
 
   call writefile(g:vundle_log, g:vundle_log_file)