Some fixes to the pager.

We didn't send any flags to the pager, as a result ansi codes
were not applied unless the user had properly set up their LESS
env variable. This was often not the case, resulting in broken
and ugly output. This commit sends along the proper flags whenever
we use the pager, regardless of the user's LESS variable

lib/pry/pager.rb

@@ -24,7 +24,12 @@ class Pry::Pager
   end
 
   def self.page_size
-    27
+    @page_size ||= begin
+      require 'io/console'
+      $stdout.winsize.first
+    rescue
+      27
+    end
   end
 
   def initialize(text)
@@ -47,13 +52,27 @@ class Pry::Pager
 
   class SystemPager < Pry::Pager
     def self.default_pager
-      ENV["PAGER"] || "less -R -S -F -X"
+      pager = ENV["PAGER"] || ""
+
+      # Default to less, and make sure less is being passed the correct options
+      if pager.strip.empty? or pager =~ /^less\s*/
+        pager = "less -R -S -F -X"
+      end
+
+      pager
     end
 
     def self.available?
-      pager_executable = default_pager.split(' ').first
-      `which #{ pager_executable }`
-    rescue
+      if @system_pager.nil?
+        @system_pager = begin
+          pager_executable = default_pager.split(' ').first
+          `which #{ pager_executable }`
+        rescue
+          false
+        end
+      else
+        @system_pager
+      end
     end
 
     def initialize(*)