Fix problem that Module#const_get might try to lookup the constant in the ancestor class, and fixing the strange error from Rails 2.3.x dependency management

Closes #478

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

Change plugin initialization to rails3 style

Change plugin initialization to rails3 style

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.

Remove Rails 3.1 `read_inheritable_attribute` deprecation and add .rvmrc to gitignore.