quick aws-s3 -> aws-sdk switch out
replace a few other access methods with the proper analogy.
remove class-variables. config goes into instance variables now.
s3 backend auth config fix.
removing some bad class methods
restore encryption parameter.
update Gemfile for security
small fixes to tests for s3.
restoring global s3 config, mistakenly removed early.
a little documentation on how to run the s3 tests
cherrypicked 59f114b1a8203db6f586960490958661d1517c77
copying fixes for tests on master branch.

a few changes required to get the tests for s3 to run.

fixed some tests.
silenced a few tests that won't be fixed (have always been broken).
removed deprecated :type column from schema.
fixed a few tests in the latest patch.
add test to exercise `url_for`
cloudfiles test pass
Merge pull request #8 from zendesk/jstillwell/feature/aws-sdk

Switch attachment_fu from using aws-s3 to aws-sdk