fix: move fmriprep-docker installation to installation page

Author: oesteban

docs/docker.rst

@@ -23,15 +23,8 @@ command line, or you can use a lightweight wrapper we created for convenience.
 
 Running *fMRIPrep* with the ``fmriprep-docker`` wrapper
 -------------------------------------------------------
-This is the easiest way to run *fMRIPrep*.
-The `Docker wrapper`_ script is a command that allows 
-you to write your command line as if you were running ``fmriprep`` directly,
-and converts it into a ``docker`` command.
-The wrapper just requires Python and an Internet connection.
-Install the wrapper using a Python distribution system, e.g.::
-
-    $ pip install --user --upgrade fmriprep-docker
-
+Before starting, make sure you
+`have the wrapper installed <installation.html#the-fmriprep-docker-wrapper>`__.
 When you run ``fmriprep-docker``, it will generate a Docker command line for you,
 print it out for reporting purposes, and then execute it without further action
 needed, e.g.::

docs/installation.rst

@@ -16,7 +16,6 @@ see :ref:`usage` for details.
 
 Container technologies: Docker and Singularity
 ==============================================
-
 Container technologies are operating-system-level virtualization methods to run Linux systems
 using the host's Linux kernel.
 This is a lightweight approach to virtualization, as compares to virtual machines.
@@ -26,7 +25,6 @@ This is a lightweight approach to virtualization, as compares to virtual machine
 
 Docker (recommended for PC/laptop and commercial Cloud)
 -------------------------------------------------------
-
 Probably, the most popular framework to execute containers is Docker.
 If you are to run *fMRIPrep* on your PC/laptop, this is the RECOMMENDED way of execution.
 Please make sure you follow the `Docker installation`_ instructions.
@@ -62,6 +60,18 @@ and `check out our documentation <docker.html>`_ to run the *fMRIPrep* image.
 The list of Docker images ready to use is found at the `Docker Hub`_, 
 under the ``poldracklab/fmriprep`` identifier.
 
+The ``fmriprep-docker`` wrapper
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+This is the easiest way to `run fMRIPrep using Docker
+<docker.html#running-fmriprep-with-the-fmriprep-docker-wrapper>`__.
+The `Docker wrapper`_ is a Python script that operates the Docker Engine seamlessly
+as if you were running ``fmriprep`` directly.
+To that end, ``fmriprep-docker`` reinterprets the command-line you are passing and
+converts it into a ``docker run`` command.
+The wrapper just requires Python and an Internet connection.
+Install the wrapper using a Python distribution system, e.g.::
+
+    $ python -m pip install --user --upgrade fmriprep-docker
 
 Singularity (recommended for HPC)
 ---------------------------------