add readme text

Author: hjacobs

README.rst

@@ -2,9 +2,16 @@
 NSEnter
 =======
 
+This Python package allows entering Linux kernel namespaces (mount, IPC, net, PID, user and UTS) by doing the "setns" syscall.
+The command line interface tries to be similar to the nsenter_ C program.
+
 Requires Python 3.4.
 
-Install::
+Install from PyPI::
+
+    sudo pip3 install nsenter
+
+Install from git source::
 
     python3 setup.py install
 
@@ -13,3 +20,4 @@ Example usage::
     docker run -d --name=redis -t redis
     sudo nsenter --all --target=`docker inspect --format '{{ .State.Pid }}' redis` /bin/bash
 
+.. _nsenter: http://man7.org/linux/man-pages/man1/nsenter.1.html