Needs work for S3 Attachments.

Fixes #738

This adds functionality to add additional params to the querystring for
S3 expiring URLs. The reason for this is if you want to override
response_content_type or response_content_disposition with expiring
URLs, you have to change Amazon's signature, which gets signed before
adding additional options to the querystring. Because it's added later,
and because Amazon's signature includes the full URL, the signature is
bad and the request fails.

To use this feature:

    has_attached_file :avatar,
                      :s3_url_options => { :response_content_disposition => "inline" }

Additionally, you can pass a lambda and it'll be evaluated when the URL
is generated. If, for example, the content type is incorrect in Amazon
(either empty or application/octet-stream), you can effectively cast the
response from Amazon as a particular content type.

    has_attached_file :avatar,
                      :s3_url_options => lambda {|model| { :response_content_type => model.avatar_content_type } }

Fixes #743

Fixes #703

There was some problem with command line parsing with a special character.

The original commit came from @amazonwebservices and @trevorrowe in #579.
I had to revise the commit and make sure all the test cases are passing.
All credits still goes to those guys, thanks a lot!

ones (:private and :public_read) in the s3_test
completed test for lambda permission value

formulate assert conditions

bit of work

Paperclip::InterpolatedString will ensure that we're not double escape the string, which was the cause of the escaped filename problem in #path method.

It's Paperclip's responsibility to escape special characters from the URL to make sure that it's comply with standard.

Closes #577, Closes #563, and reverse my judgement on #482.

It was working fine for me locally