Determine color usage dynamically

This changes the color usage to be determined dynamically. Prior to this
the config was always read. That meant that if the scenario was ever
written to disk (using save_configuration), it stored the value of
colors_possible? and uses that indefinitely.

After this change, the value of colors will remain nil (determined at
runtime) until the user uses --[no-]colors, which is then persisted.

lib/kafo/configuration.rb

@@ -26,7 +26,7 @@ class Configuration
  ScenarioOption::ANSWER_FILE => './config/answers.yaml',
  ScenarioOption::INSTALLER_DIR => '.',
  ScenarioOption::MODULE_DIRS => ['./modules'],
- ScenarioOption::COLORS => Kafo::ColorScheme.colors_possible?,
+ ScenarioOption::COLORS => nil,
  ScenarioOption::COLOR_OF_BACKGROUND => :dark,
  ScenarioOption::HOOK_DIRS => [],
  ScenarioOption::CHECK_DIRS => nil,
@@ -107,6 +107,10 @@ def app
  end
  end
 
+ def use_colors?
+ app.fetch(ScenarioOption::COLORS) { Kafo::ColorScheme.colors_possible? }
+ end
+
  def get_custom(key)
  custom_storage[key.to_sym]
  end

lib/kafo/kafo_configure.rb

@@ -77,12 +77,14 @@ def help(*args)
 
  def use_colors?
  if config
- colors = config.app[:colors]
+ config.use_colors?
+ elsif ARGV.include?('--no-colors')
+ false
+ elsif ARGV.include?('--colors')
+ true
  else
- colors = ARGV.include?('--no-colors') ? false : nil
- colors = ARGV.include?('--colors') ? true : nil if colors.nil?
+ Kafo::ColorScheme.colors_possible?
  end
- colors
  end
 
  def preset_color_scheme
@@ -190,7 +192,7 @@ def execute
  parse_cli_arguments
 
  if !config.app[:verbose]
- @progress_bar = config.app[:colors] ? ProgressBars::Colored.new : ProgressBars::BlackWhite.new
+ @progress_bar = config.use_colors? ? ProgressBars::Colored.new : ProgressBars::BlackWhite.new
  end
 
  unless skip_checks_i_know_better?
@@ -347,7 +349,7 @@ def terminal_log_levels_message
 
  def set_app_options
  app_option ['--[no-]colors'], :flag, 'Use color output on STDOUT',
- :default => config.app[:colors], :advanced => true
+ :default => config.use_colors?, :advanced => true
  app_option ['--color-of-background'], 'COLOR', 'Your terminal background is :bright or :dark',
  :default => config.app[:color_of_background], :advanced => true
  app_option ['--dont-save-answers'], :flag, "Skip saving answers to '#{self.class.config.answer_file}'?",