Added auto lang listing and CONTRIBUTING.md

Added a small framework for easily updating a list of all languages the repository contains a "Hello World" program in. See CONTRIBUTING.md for a command for updating the listing (using the list_langs.rb Ruby script).

list_langs.rb

@@ -0,0 +1,13 @@
+Dir.foreach "." do |odir|
+  next if odir == "." or odir == ".." or not File.directory?(odir)
+  Dir.foreach odir do |dir|
+    next if dir == "." or dir == ".."
+    currdirname = ""
+    dir.split(".")[0].gsub("-", " ").split(" ").each do |str|
+      currdirname << str.capitalize + " "
+    end
+    currdirname.chomp(currdirname[-1])
+    puts "* #{currdirname}"
+  end
+end
+