Don’t escape '/' characters in keys

Add test for this behaviour
Add support for canonicalising AWS keys

We don’t just need to URL escape them, they need to be Unicode normalised too http://tools.ietf.org/html/rfc3987#section-5.3.2.2
Fix the Unicode strings for Ruby 1.8.7

Can’t use \u{xxxx} :(
Pack takes Unicode characters, not UTF-8 encodings
Merge branch 'master' into fix-aws-escape
Merge pull request #2110 from github/fix-aws-escape

Fix aws escape