docs: document units better

docs/units.rst

@@ -5,6 +5,10 @@ By default, Squib thinks in pixels. This decision was made so that we can have p
 
 Here are some examples, which `lives here <https://github.com/andymeneely/squib/tree/master/samples/units.rb>`_
 
-.. literalinclude:: ../samples/units.rb
+.. literalinclude:: ../samples/units/_units.rb
   :language: ruby
   :linenos:
+
+.. raw:: html
+
+  <img src="units/units_00_expected.png">

samples/units/_units.rb

@@ -1,7 +1,7 @@
 require 'squib'
 
 Squib::Deck.new(width: '1.5in', height: '1.5in') do
-  background color: '#ddd'
+  background color: :white
 
   # We can use our DSL-method to use inches
   # Computed using @dpi (set to 300 by default)

spec/data/samples/units/_units.rb.txt

@@ -1,6 +1,6 @@
 cairo: antialias=(["subpixel"])
 cairo: save([])
-cairo: set_source_color(["#ddd"])
+cairo: set_source_color(["white"])
 cairo: paint([])
 cairo: restore([])
 cairo: save([])