Add a little more info to Mac guide, a=chris

diff --git a/en-US/pages/install.thtml b/en-US/pages/install.thtml
index fae9350..bcc17f1 100755
--- a/en-US/pages/install.thtml
+++ b/en-US/pages/install.thtml
@@ -389,6 +389,17 @@ the Yioop folder to yioop.</li>
 sudo mkdir /Library/WebServer/Documents/yioop_data
 sudo chmod 777 /Library/WebServer/Documents/yioop_data
 </pre>
+You probably want to make sure Spotlight (Mac's built-in file and folder
+indexer) doesn't index this folder -- especially during a crawl -- or you
+system might really slow down. To prevent this open Control Panel, choose
+Spotlight, select the Privacy tab, and add the above folder to the list
+of folder Spotlight shouldn't index. If you are storing crawls on an
+external drive, you might want to make sure that drive gets automounted
+without a login, in the event of a power failure that exceeds your backup power
+supply time. To do this you can write the preference:
+<pre>
+sudo defaults write /Library/Preferences/SystemConfiguration/autodiskmount AutomountDisksWithoutUserLogin -bool true
+</pre>
 </li>
 <li>In a browser, go to the page http://localhost/yioop/ .
 You should see a configure screen