Add ability to specify ".allowing" and ".rejecting" individually with content_type validation matcher.

Closes #472, Closes #532

Closes #515

option to convert.

Closes #170

added :preserve_files option so paperclip can get along with soft-delete plugins like acts_as_paranoid

Closes #152

Closes #62

Closes #214

Example:
  has_attached_file :image,
    :bucket => "testing",
    :path => ":attachment/:style/:basename.:extension"
    :s3_permissions => {
      :original => :private
    },
    :styles => {
      :thumb => '80x80>'
    }

The above will allow public read access on :thumb but require credentials for :original.

Example of setting default to private:
  has_attached_file :image,
    :bucket => "testing",
    :path => ":attachment/:style/:basename.:extension"
    :s3_permissions => :private
    :styles => {
      :thumb => '80x80>'
    }

The above will set all to private

Closes #398

Closes #499

the :default_url option for has_attached_file can now also be a Proc/lamba, which gets executed *before* it gets interpolated

Closes #253, Closes #360

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. :)

This addresses an issue where Paperclip can indefinitely block execution
of an application by telling ImageMagick to "identify -format %wx%h [0]"
which will then wait for input from STDIN forever.

don't needlessly retrieve directory and contents from fog provider. create the directory only when it's needed.

Conflicts:

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