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

fog.gemspec

@@ -50,6 +50,7 @@ Gem::Specification.new do |s|
   s.add_dependency('net-ssh', '>=2.1.3')
   s.add_dependency('nokogiri', '~>1.5')
   s.add_dependency('ruby-hmac')
+  s.add_dependency('unicode', "~> 0.4.4")
 
   ## List your development dependencies here. Development dependencies are
   ## those that are only needed during development

lib/fog/aws.rb

@@ -1,6 +1,7 @@
 require 'fog/core'
 require 'fog/aws/credential_fetcher'
 require 'fog/aws/signaturev4'
+require 'unicode'
 module Fog
   module AWS
     extend Fog::Provider
@@ -84,6 +85,7 @@ module Fog
     end
 
     def self.escape(string)
+      string = Unicode::normalize_C(string)
       string.gsub(/([^a-zA-Z0-9_.\-~\/]+)/) {
         "%" + $1.unpack("H2" * $1.bytesize).join("%").upcase
       }

tests/aws/signed_params_tests.rb

@@ -6,4 +6,12 @@ Shindo.tests('AWS | signed_params', ['aws']) do
   tests('Keys can contain a hierarchical prefix which should not be escaped') do
     returns( Fog::AWS.escape( "key/with/prefix" ) ) { "key/with/prefix" }
   end
+
+  tests('Keys should be canonicalised using Unicode NFC') do
+    returns( Fog::AWS.escape( "\u{00e9}" ) ) { "%C3%A9" }
+
+    tests('Characters with combining mark should be combined and then escaped') do
+      returns( Fog::AWS.escape( "\u{0065}\u{0301}" ) ) { "%C3%A9" }
+    end
+  end
 end