Fix indent of the code embeded in README

Author: domitry

README.md

@@ -64,31 +64,35 @@ Therefore we use libzmq3 like the following:
 1. make your ports tree up-to-date.
 2. replace LIBDEPENDS line in ports/net/py-pyzmq/Makefile
 
+    ```shell
     LIB_DEPENDS=    libzmq.so:${PORTSDIR}/net/libzmq4
-
-with
-
+    ```
+    with
+    ```shell
     LIB_DEPENDS=    libzmq.so:${PORTSDIR}/net/libzmq3
-
+    ```
 3. install related packages
 
+    ```shell
     $ sudo pkg install libzmq3 py27-qt4-gui py27-pexpect-3.3 py27-qt4-svg py27-pygments py27-Jinja2 py27-tornado py27-jsonschema
-
+    ```
 4. make install using ports
 
+    ```shell
     $ cd /usr/ports/net/py-pyzmq
     $ sudo make install
     $ cd /usr/ports/devel/ipython
     $ sudo make install
-
+    ```
 Then, install iruby and related ports and gems.
-
+    ```shell
     $ sudo pkg install rubygem-mimemagic
     $ sudo gem install ffi-rzmq  # install ffi, ffi-rzmq-core and ffi-rzmq
     $ git clone https://github.com/SciRuby/iruby.git
     $ cd iruby
     $ gem build iruby.gemspec
     $ sudo gem install iruby-0.2.7.gem
+    ```
 
 ### After the installation