Use --mime instead of --mime-type for `file` command

Thank you @excid3 for suggestion.

Closes #582

lib/paperclip/upfile.rb

@@ -25,7 +25,7 @@ module Paperclip
     def type_from_file_command
     #  On BSDs, `file` doesn't give a result code of 1 if the file doesn't exist.
       type = (self.original_filename.match(/\.(\w+)$/)[1] rescue "octet-stream").downcase
-      mime_type = (Paperclip.run("file", "-b --mime-type :file", :file => self.path).split(':').last.strip rescue "application/x-#{type}")
+      mime_type = (Paperclip.run("file", "-b --mime :file", :file => self.path).split(/[:;]\s+/)[0] rescue "application/x-#{type}")
       mime_type = "application/x-#{type}" if mime_type.match(/\(.*?\)/)
       mime_type
     end

test/fixtures/text.txt

+paperclip!

test/upfile_test.rb

@@ -34,4 +34,20 @@ class UpfileTest < Test::Unit::TestCase
     end
     assert_equal 'text/plain', file.content_type
   end
+
+  { '5k.png'       => 'image/png',
+    'animated.gif' => 'image/gif',
+    'text.txt'     => 'text/plain',
+    'twopage.pdf'  => 'application/pdf'
+  }.each do |filename, content_type|
+    should "return a content type of #{content_type} from a file command for file #{filename}" do
+      file = File.new(File.join(File.dirname(__FILE__), "fixtures", filename))
+      class << file
+        include Paperclip::Upfile
+      end
+
+      assert_equal content_type, file.type_from_file_command
+    end
+  end
+
 end