Starting paint args class - not integrated yet.

Draw args also now requires custom_colors from Deck. (Can't trust caller to override the default.)

spec/args/paint_spec.rb

@@ -0,0 +1,22 @@
+require 'spec_helper'
+require 'squib/args/paint'
+
+describe Squib::Args::Draw do
+  let(:custom_colors) { {'foo' => 'abc'} }
+  subject(:paint)      {Squib::Args::Paint.new(custom_colors)}
+
+  context 'alpha' do
+
+    it 'can be a float' do
+      args = {alpha: 0.6}
+      paint.load!(args)
+      expect(paint.alpha).to eq [0.6]
+    end
+
+    it 'raises exception when not a float' do
+      args = {alpha: /6/}
+      expect { paint.load!(args) }.to raise_error('alpha must respond to to_f')
+    end
+
+  end
+end