Merge pull request #35 from ntavares/ipsec-psk-rules

Be explicit in regards to OpenSwan ipsec.secrets rule.According to:
http://linux.die.net/man/5/ipsec.secrets

A preshared secret is most conveniently represented as a sequence of characters, delimited by the double-quote character ("). The sequence cannot contain a newline or double-quote.

* pr/35:
  Be explicit in regards to OpenSwan ipsec.secrets rule.

Signed-off-by: Rohit Yadav <rohit.yadav@shapeblue.com>
diff --git a/source/networking/site_to_site_vpn.rst b/source/networking/site_to_site_vpn.rst
index 34ec0a9..3049396 100644
--- a/source/networking/site_to_site_vpn.rst
+++ b/source/networking/site_to_site_vpn.rst
@@ -77,7 +77,7 @@
    -  **IPsec Preshared Key**: Preshared keying is a method where the
       endpoints of the VPN share a secret key. This key value is used to
       authenticate the customer gateway and the VPC VPN gateway to each
-      other.
+      other. The sequence cannot contain a newline or double-quote.
 
       .. note:: 
          The IKE peers (VPN end points) authenticate each other by