[WIP] Implement subroutine opcodes

Author: Peppece

docs/contributing.rst

@@ -6,13 +6,7 @@ Thank you for your interest in contributing! We welcome all contributions no mat
 Setting the stage
 ~~~~~~~~~~~~~~~~~
 
-**Only on macOS**: if it is the first time you install Py-EVM, you will need to install LevelDB with brew before taking the following steps:
-
-.. code:: sh
-
-    brew install python3 LevelDB
-
-
+.. note::If it is the first time you install py-evm on a macOS, check https://py-evm.readthedocs.io/en/latest/guides/quickstart.html#installing-on-macos
 
 We need to clone the Py-EVM repository. Py-EVM depends on a submodule of the common tests across all clients, so we need to clone the repo with the ``--recursive`` flag. Example:
 

docs/guides/quickstart.rst

@@ -37,11 +37,11 @@ Finally, we can install the ``py-evm`` package via pip.
 Installing on macOS
 -------------------
 
-First, install Python 3 with brew:
+First, install Python 3 and LevelDB with brew:
 
 .. code:: sh
 
-  brew install python3
+  brew install python3 leveldb
 
 .. note::
   .. include:: /fragments/virtualenv_explainer.rst