clarify that java is optional in the docs

Author: kripken

site/source/docs/building_from_source/building_emscripten_from_source_on_windows.rst

@@ -44,7 +44,7 @@ These instructions explain how to install **all** the :ref:`required tools <tool
 
 #. Install `Github for Windows <http://windows.github.com/>`_ (or any other git client).
 
-#. Install `Java <http://java.com/en/download/index.jsp>`_.
+#. Install `Java <http://java.com/en/download/index.jsp>`_ (Java is optional, you only need it for Closure Compiler minification).
 
 #. Build :ref:`Fastcomp <LLVM-Backend>` (LLVM + Clang) from source using :ref:`these instructions <building-fastcomp-from-source>`. 
 

site/source/docs/getting_started/downloads.rst

@@ -154,7 +154,7 @@ Linux
 		# Install node.js
 		sudo apt-get install nodejs
 		
-		# Install Java
+		# Install Java (optional, only needed for Closure Compiler minification)
 		sudo apt-get install default-jre
 
 .. note:: Your system may provide Node.js as ``node`` instead of ``nodejs``. In that case, you may need to also update the ``NODE_JS`` attribute of your ``~/.emscripten`` file.