DO NOT MERGE. Update readme to reflect addition of SEPOLICY_IGNORE.

Change-Id: I427c0f4828d45f2c43206c09cb37e3eb30455dee
diff --git a/README b/README
index e9f37a1..83ee7a2 100644
--- a/README
+++ b/README
@@ -3,7 +3,7 @@
 Additional, per device, policy files can be added into the
 policy build.
 
-They can be configured through the use of three variables,
+They can be configured through the use of four variables,
 they are:
 1. BOARD_SEPOLICY_REPLACE
 2. BOARD_SEPOLICY_UNION