Fix support for legacy terminals (Urxvt)

Thanks to u/katie-is-gay for tracking this down:
https://www.reddit.com/r/archlinux/comments/cnvlsa/lolcat_colors_glitched_only_at_urxvt/ewelhfn

And to @incomingstick for reporting it:
busyloop#99

Also thanks to @XVilka for maintaining an absurdly
comprehensive guide on Truecolor terminal support:
https://gist.github.com/XVilka/8346728

TLDR: We no longer rely on 24bit auto-detection by the Paint gem.
Lolcat now performs its own detection and otherwise defaults 256 colors.

The auto-detection is only a qualified guess.
Use the -t flag to ensure highest rainbow fidelity.

Fixes busyloop#97

lib/lolcat/lol.rb

@@ -30,8 +30,8 @@ module Lol
   ANSI_ESCAPE = /((?:\e(?:[ -\/]+.|[\]PX^_][^\a\e]*|\[[0-?]*.|.))*)(.?)/m
   INCOMPLETE_ESCAPE = /\e(?:[ -\/]*|[\]PX^_][^\a\e]*|\[[0-?]*)$/
 
-  @paint_detected_mode = Paint.detect_mode
   @os = 0
+  @paint_init = false
 
   def self.rainbow(freq, i)
      red   = Math.sin(freq*i + 0) * 127 + 128
@@ -78,7 +78,7 @@ def self.println(str, defaults={}, opts={})
 
   def self.println_plain(str, defaults={}, opts={}, chomped)
     opts.merge!(defaults)
-    set_mode(opts[:truecolor])
+    set_mode(opts[:truecolor]) unless @paint_init
     filtered = str.scan(ANSI_ESCAPE)
     filtered.each_with_index do |c, i|
       color = rainbow(opts[:freq], @os+i/opts[:spread])
@@ -113,7 +113,10 @@ def self.println_ani(str, opts={}, chomped)
   end
 
   def self.set_mode(truecolor)
-    @paint_mode_detected ||= Paint.mode
+    # @paint_mode_detected = Paint.mode
+    @paint_mode_detected = %w[truecolor 24bit].include?(ENV['COLORTERM']) ? 0xffffff : 256
     Paint.mode = truecolor ? 0xffffff : @paint_mode_detected
+    STDERR.puts "DEBUG: Paint.mode = #{Paint.mode} (detected: #{@paint_mode_detected})" if ENV['LOLCAT_DEBUG']
+    @paint_init = true
   end
 end

lib/lolcat/version.rb

@@ -1,3 +1,3 @@
 module Lolcat
-  VERSION = "99.9.99"
+  VERSION = "100.0.0"
 end

lolcat.gemspec

@@ -12,7 +12,7 @@ Gem::Specification.new do |s|
   s.summary     = %q{Okay, no unicorns. But rainbows!!}
 
   s.add_development_dependency "rake"
-  s.add_dependency "paint", "~> 2.0.0"
+  s.add_dependency "paint", "~> 2.1.0"
   s.add_dependency "optimist", "~> 3.0.0"
   s.add_dependency "manpages", "~> 0.6.1"