Update README.

README.md

@@ -29,8 +29,15 @@ wish to interface with the Linux iptables framework..
 
 ![buildstatus](https://travis-ci.org/ldx/python-iptables.png?branch=master)
 
-Compiling and installing
-------------------------
+Installing via pip
+------------------
+
+The usual way:
+
+    pip install --upgrade python-iptables
+
+Compiling from source
+---------------------
 
 First make sure you have iptables installed (most Linux distributions
 install it by default). `Python-iptables` needs the shared libraries