Add Requirements to README

Author: kojix2

README.md

@@ -7,10 +7,12 @@
 IRuby is a Ruby kernel for [Jupyter project](http://try.jupyter.org/).
 
 ## Installation
-How to set up [ZeroMQ](http://zeromq.org/) depends on your environment.
-You can use one of the following libraries.
-* [ffi-rzmq](https://github.com/chuckremes/ffi-rzmq) and [libzmq](https://github.com/zeromq/libzmq) >= 3.2
-* [CZTop](https://gitlab.com/paddor/cztop) and [CZMQ](https://github.com/zeromq/czmq) >= 4.0.0
+
+### Requirements
+* [Jupyter](https://jupyter.org)
+* One of the following is required
+    * [ffi-rzmq](https://github.com/chuckremes/ffi-rzmq) and [libzmq](https://github.com/zeromq/libzmq)
+    * [CZTop](https://gitlab.com/paddor/cztop) and [CZMQ](https://github.com/zeromq/czmq)
 
 We recommend the [Pry](https://github.com/pry/pry) backend for full functionality.