Fix messages for skipped bundled gems

Author: nobu

tool/rbinstall.rb

@@ -1187,7 +1187,8 @@ class << (w = [])
     skipped.default = "not found in bundled_gems"
     puts "skipped bundled gems:"
     gems.each do |gem|
-      printf "    %-32s%s\n", File.basename(gem), skipped[gem]
+      gem = File.basename(gem)
+      printf "    %-31s %s\n", gem, skipped[gem.chomp(".gem")]
     end
   end
 end