HighLine：HighLine.use_color?, .use_color=

>> require "highline/import"
=> true
>> ft = HighLine::ColorScheme.new {|cs| cs[:headline] = [ :bold, :yellow, :on_black ]}
=> #<HighLine::ColorScheme:0xb79cbc44 @scheme={"headline"=>["\e[1m", "\e[33m", "\e[40m"]}>
>> HighLine.color_scheme = ft
=> #<HighLine::ColorScheme:0xb79cbc44 @scheme={"headline"=>["\e[1m", "\e[33m", "\e[40m"]}>
>> HighLine.use_color?
=> true
>> HighLine.new.color("foo")
=> "foo\e[0m"
>> HighLine.use_color = false
=> false
>> HighLine.use_color?
=> false
>> HighLine.new.color("foo")
=> "foo"