Add UpgradeSignatureToEncryptionCookieStore

This allows easy upgrading from the old signed Cookie Store <= 3.2
or the deprecated one in 4.0 (the ones that doesn't use key derivation)
to the new one that signs using key derivation
Revert "add AR deep dive video links to guides"

This reverts commit 25648ce35b9d8df9fac81c1d53c45aaeef08fde9.
Revert "Switch to 1.9 hash syntax"

This reverts commit d8596c4b8500a899d686c57fa093c549b0378c7a.

Reason: too many mistakes [ci skip]
remove kindle link from guides index [ci skip]
copy edits and fixes [ci skip]
Merge branch 'master' of github.com:lifo/docrails

Conflicts:
	actionpack/lib/action_dispatch/routing/redirection.rb
Remove old comments about using our own sdoc fork [ci skip]
Improve UpgradeSignatureToEncryptionCookieStore docs

I suck at English, please help me reviewing this <3 <3 <3
[ci skip]
Revert "mysql does not build on Ruby 2.0.0 at the moment"

This reverts commit 8d8fd13179cacd86f307e87396474bdfab9f3462.

mysql 2.8.1 gem can be built on ruby 2.0.0-preview1.
Merge pull request #8244 from yahonda/mysql_ruby200

Now mysql gem can be built on ruby 2.0.0-preview1
Test for has_many bug on unsaved records

See issue #7950.
Fix some AR changelog entries [ci skip]
Revert "Debugger gem doesn't work with patchlevel >= 327"

This reverts commit 0ecd4640664c4723323d6fff5760dc4d833d7eb9.
Adding sqlserver.yml template to satisfy "-d sqlserver" being given
invocations of "rails new".
Merge pull request #8247 from rnesius/sqlserver-template

Adding sqlserver.yml template to satisfy "-d sqlserver" 
Removed extra call to #diff in #assert_recognizes. assert_equal calls it for you and shows the diff. Also delayed message calculation so the cost of the diff on success is now gone.
Please use assert_equal instead of diff directly
Merge pull request #8248 from zenspider/master

Removed extra call to #diff in #assert_recognizes
Add Ruby 2.0 to .travis.yml.

@joshk said it's okay. :)
Merge pull request #8249 from steveklabnik/add_two_oh_to_travis

Add Ruby 2.0 to .travis.yml.