There's a case when you really don't want to make a thumbnail of only the first frame, such as making thumbnail for GIF image. This patch will check that the source and output format is an animated format, and not calling `[0]` on it.

Closes #454

Change S3 storage behavior to get the content_type for each upload, rather than only the original file. This prevents a still frame from a video or a conversion of a file from being served with the original mimetype.

Closes #38, #129

`convert` will pick this up automatically. :)

In Rails 3, Paperclip gem being loaded before the Rails object is properly configured and causing those processors not get require'd. This patch should fix that by lazy-loaded the processor.

Closes #206, #233, #247, #480, #494

Closes #481

Conflicts:

	lib/paperclip/storage/s3.rb
	test/storage_test.rb