add informations about guest user

assets/html/documentation.html

@@ -72,6 +72,12 @@
 				<p>
 				Another step on the way. Now basic signup is possible.
 				Users and credential will be stored in gdbm files.
+				If you do not want to signup you can use the pre created
+				guest account to login.<br/><br/>
+				<b>username:</b> guest<br/>
+				<b>password:</b> guest<br/><br/>
+				This user will not be available if you build your own
+				version of taskrambler.
 				</p>
 
 				<h3>Usage</h3>