Respect DPI settings in text, add pt unit

This has the compatibility impact that all font sizes should be divided by 3 to maintain their same sizes.

Based on PR #225. Thanks @felixleong!!

Conflicts:
	bin/squib
	lib/squib/graphics/text.rb

samples/ranges/_ranges.rb

@@ -7,12 +7,12 @@ data = { 'name' => ['Thief', 'Grifter', 'Mastermind'],
 Squib::Deck.new(width: 825, height: 1125, cards: 3) do
   # Default range is :all
   background color: :white
-  text str: data['name'], x: 250, y: 55, font: 'Arial 54'
-  text str: data['level'], x: 65, y: 40, font: 'Arial 72'
+  text str: data['name'], x: 250, y: 55, font: 'Arial 18'
+  text str: data['level'], x: 65, y: 40, font: 'Arial 24'
 
   # Could be explicit about using :all, too
   text range: :all,
-       str: data['type'], x: 40, y: 128, font: 'Arial 18',
+       str: data['type'], x: 40, y: 128, font: 'Arial 6',
        width: 100, align: :center
 
   # Ranges are inclusive, zero-based