add setup instructions

README.md

@@ -2,9 +2,10 @@
 
 [![Slack](https://img.shields.io/badge/join-slack-e32072.svg?style=flat)](http://slack.blockstack.org/)
 
-Virtualchain is a Python library for processing and maintaining virtual blockchains.
+Virtualchain is a Python 2.7 library for processing and maintaining virtual blockchains.
+
+## What is a virtual blockchain?
 
-### What is a virtual blockchain?
 ![Virtual Blockchain](https://blockstack.org/images/article-diagrams/virtual-blockchain.png)
 
 A *virtual blockchain* is a layer that sits on top of a blockchain that introduces new functionality and operations without requiring changes to the underlying blockchain. The nodes of the underlying blockchain network are not aware of the presence of virtual blockchains. New operations are defined in the virtual blockchain layer and are encoded in the metadata of valid blockchain transactions. Blockchain nodes do see the raw transactions, but the logic for processing the virtual blockchain operations only exists at the virtual blockchain level.
@@ -16,3 +17,22 @@ In a sense, a virtual blockchain is a state machine on top of an underlying bloc
 One way to think of these state machines is as standalone smart contracts. When defining state machines with the Virtualchain library, programmers have the flexibility and boundless potential at their fingertips that they do when working with a Turing complete smart contract system, and at the same time, once a state machine is defined and operational, developers have the benefits of working with a specialized and operationally-efficient environment.
 
 You can read more about the design and implementation of this library in our [DCCL 2016 paper](https://blockstack.org/virtualchain_dccl16.pdf).
+
+## Installation
+
+This package provides the `virtualchain` Python package.  To install from
+source, do the following:
+
+```
+$ git clone https://github.com/blockstack/virtualchain
+$ cd virtualchain
+$ python2 ./setup.py build
+$ sudo python2 ./setup.py install
+```
+
+This package is also available via `pip`.  Be sure that your `pip` is configured
+to install packages for Python 2.7.x.
+
+```
+$ pip install virtualchain
+```