Update README and Makefile.

README

@@ -8,17 +8,31 @@ Requirements
 In order to build slock you need the Xlib header files.
 
 
+Notes
+------------
+As of right now, this implementation assumes that the user has no automatic
+display management utilities, like mutter.
+
+
 Installation
 ------------
-Edit config.mk to match your local setup (slock is installed into
-the /usr/local namespace by default).
-
-Afterwards enter the following command to build and install slock
-(if necessary as root):
-
-    make clean install
+# make
+# chmod u+s ./slock
+# mv ./slock /usr/local/bin
 
 
 Running slock
 -------------
 Simply invoke the 'slock' command. To get out of it, enter your password.
+
+
+Security Considerations
+-------------
+To  make sure a locked screen can not be bypassed by switching VTs or killing
+the X server with Ctrl+Alt+Backspace, it is recommended to disable both in
+xorg.conf for maximum security:
+
+Section "ServerFlags"
+    Option "DontVTSwitch" "True"
+    Option "DontZap"      "True"
+EndSection