Allow overriding the path with :orignal_filename

When passing a multipart uploaded file to wand it is generally
a temp file with no extension leaving MIME with no way to detect
the type.

lib/wand.rb

@@ -3,8 +3,8 @@
 module Wand
   Version = '0.2.1'
 
-  def self.wave(path)
-    type = MIME::Types.type_for(path)[0].to_s
+  def self.wave(path, options={})
+    type = MIME::Types.type_for(options[:original_filename] || path)[0].to_s
     type = execute_file_cmd(path).split(';')[0].strip if type.nil? || type == ''
     type = nil if type =~ /cannot\sopen/
     type
@@ -21,4 +21,4 @@ def self.executable=(path)
   def self.execute_file_cmd(path)
     `#{executable} --mime --brief #{path}`
   end
-end
+end

test/test_wand.rb

@@ -32,6 +32,10 @@ class TestWand < Test::Unit::TestCase
       end
     end
 
+    should "return value from mime type when original_filename provided" do
+      assert_equal 'audio/mpeg', Wand.wave('some_temp_file', :original_filename => 'test.mp3')
+    end
+
     should "return nil when mime type and file fail" do
       assert_nil Wand.wave('AVGARDD.eot')
     end