Add get_file_extname method

lib/thumbnail/formats.rb

 module Thumbnail
   module Formats
 
-    def get_file_format file
+    def get_file_basename file
       unless file.nil?
-        file_format = File.extname(file)
+        file_format = File.basename(file)
       else
         file_format = ""
       end
       file_format
     end
 
+    def get_file_extname file
+      unless file.nil?
+        file_name = File.extname(file)
+      else
+        file_name = ""
+      end
+      file_name
+    end
+
     def array_to_upcase array
       upcase_array = []
       array.each do |a|