Update copyright to 2013
Merge pull request #1125 from thoughtbot/ap-update-copyright-to-2013

Update copyright to 2013
Updating Cocaine to ~> 0.5.0 to get latest fixes
Merge pull request #1139 from johnnyshields/master

Updating Cocaine to ~> 0.5.0 to get latest fixes
Lockfile update
Cache pluralizations in interpolations for speed
Fix logo link

Update link to thoughtbot logo using new public image.
:s3_host_name can be a proc
Fix Paperclip's io_adapters to properly sanitize original_filename

The ":" is a special character in file paths passed to ImageMagick's
"identify" command. Even though Cocaine (and everything else in
paperclip) escapes special characters correctly, we need to strip it out
of filenames to ensure identify (and probably other ImageMagick
commands) can run correctly.
Bump up version of aws-sdk dependency
Accept and pass :credential_provider option to AWS-SDK
Make configuration of :s3_credentials optional

Since AWS-SDK 1.5.3 [1] the library automatically checks for credentials.
This makes it unnecessary to supply credentials when they are present
in environment variables or supplied via an IAM Instance Profile.

[1] http://aws.amazon.com/releasenotes/Ruby/0304005114813505
Add test for supplying :s3_credentials in an unsupported manor
Lower requirement of aws-sdk to 1.5.7
Fix s3 writes with style procs

S3#flush_writes was accessing the styles option without checking for a
proc. We can just use the instance's styles method to have it done for
us.
Refactor style specific headers code

Allow either a hash or a Style object to set the headers.
Add default_url option to Quick Start example

It took me a lot of digging to figure out how to add the
`:default_url` option, but it seems a common option that many
people will need to modify. Putting it anywhere in the README
will help those who just cmd-F on the page, like me.
mark instance as changed after assigning new file
Merge pull request #1169 from chadoh/patch-1

Add default_url option to Quick Start example
Reset instance attributes when clearing attachment with preserve_files