docs: include code sample for build groups

docs/build_groups.rst

@@ -9,17 +9,15 @@ Squib's Build Groups help you with these situations. By grouping your Squib code
 
 Here's a basic example:
 
-.. raw:: html
+.. literalinclude:: ../samples/build_groups/build_groups.rb
+  :language: ruby
+  :linenos:
 
-  <script type="text/javascript" src="https://ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js"></script>
-  <script type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/gist-embed/2.4/gist-embed.min.js"></script>
-  <code data-gist-id="bda48487e3b8c9d15edb" data-gist-file="build_groups.rb"></code>
-
-Only one group is enabled by default: ``:all``. All other groups are disabled by default. To see which groups are enabled currently, the :doc:`/dsl/groups` returns the set.
+Only one group is enabled by default: ``:all``. All other groups are disabled by default. To see which groups are enabled currently, the :doc:`/dsl/build_groups` returns the set.
 
 Groups can be enabled and disabled in several ways:
 
-  * The :doc:`/dsl/enable_group` and :doc:`/dsl/disable_group`  DSL methods can explicitly enable/disable a group. Again, you're back to commenting out the *enable_group* call, but that's easier than remembering what lines to comment out each time.
+  * The :doc:`/dsl/enable_build` and :doc:`/dsl/disable_build`  DSL methods can explicitly enable/disable a group. Again, you're back to commenting out the *enable_group* call, but that's easier than remembering what lines to comment out each time.
   * When a ``Squib::Deck`` is initialized, the `environment variable <https://en.wikipedia.org/wiki/Environment_variable>`_ ``SQUIB_BUILD`` is consulted for a comma-separated string. These are converted to Ruby symbols and the corresponding groups are enabled.
 
 Note that the environment variables are intended to change from run to run, from the command line (see above gist for examples in various OS's).
@@ -31,12 +29,9 @@ Note that the environment variables are intended to change from run to run, from
 Don't like how Windows specifies environment variables? One adaptation of this is to do the environment setting in a ``Rakefile``. Rake is the build utility that comes with Ruby, and it allows us to set different tasks exactly in this way. This Rakefile works nicely with our above code example:
 
 
-.. raw:: html
-
-  <script type="text/javascript" src="https://ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js"></script>
-  <script type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/gist-embed/2.4/gist-embed.min.js"></script>
-  <code data-gist-id="bda48487e3b8c9d15edb" data-gist-file="Rakefile"></code>
-
+.. literalinclude:: ../samples/build_groups/Rakefile
+  :language: ruby
+  :linenos:
 
 Thus, you can just run this code with commands like these::