[WIP] Implement subroutine opcodes

Author: Peppece

docs/contributing.rst

@@ -6,11 +6,13 @@ Thank you for your interest in contributing! We welcome all contributions no mat
 Setting the stage
 ~~~~~~~~~~~~~~~~~
 
-.. note:: If you are on macOS and it is the first time you install Py-EVM, you will need to install LevelDB with brew before taking the following steps:
+.. note::
 
-    .. code:: sh
+    If you are on macOS and it is the first time you install Py-EVM, you will need to install LevelDB with brew before taking the following steps:
 
-        brew install python3 LevelDB
+.. code:: sh
+
+    brew install python3 LevelDB