fix for 1.8.x

diff --git a/lib/termtter/system_extensions.rb b/lib/termtter/system_extensions.rb
index 8816427..d211d95 100644
--- a/lib/termtter/system_extensions.rb
+++ b/lib/termtter/system_extensions.rb
@@ -73,7 +73,7 @@ def open_browser(url)
   else
     [['xdg-open'], ['firefox'], ['w3m', '-X']]
   end.find do |cmd|
-    system *cmd, url
+    system(*(cmd + [url]))
     $?.exitstatus != 127
   end
   if found