Adding additional plugins to debugging guide [ci skip]

Thanks @lintzchiang. [ci skip]

For example:

    class Post < ActiveRecord::Base
      default_scope -> { where published: true }
    end

    class Comment
      belongs_to :post
    end

When calling `Comment.join(:post)`, we expect to receive only
comments on published posts, since that is the default scope for
posts.

Before this change, the default scope from `Post` was not applied,
so we'd get comments on unpublished posts.

Oops. We need to estalish/remove the connection in the setup/teardown,
else it messes with the fixtures.

Clearly nobody uses this except me. It's fast people!

Remove depreacted finders

Remove deprecation warning from AttributeMethodsMatcher

They were deprecated in 4.0, planned to remove in 4.1

Asking user to declare post resource in getting start guide

Remove deprecated attr_protected/accessible

Rails 4.0 has removed attr_protected and attr_accessible feature in favor of Strong Parameters.

Remove passing the prompt to grouped_options_for_select as an argument, because it was deprecated.

Fix documentation for grouped_collection_select

Re-remove deprecated API.

Removed "to:" from root directive and fixed typo ":to"

`root :to` is invalid syntax
`root to:` is valid, but the generated routes file omits `to:`

Fix copyright year for actionview [ci skip]

activerecord/examples/simple.rb use master branch activesupport gem

fix grammar, change 'an' to 'a' [ci skip]

make default value for `:message` on `AM::Errors` explicit.

Removing deprecation message and silencing method.

Use activerecord 4.0.0 for reporting bugs using the template

There was a parenthesis in the guides, which resulted in the one link not working, and a second link not even showing. [ci skip]

The deprecation rake task is no longer useful because the deprecated
methods have already been removed.

The method for silencing stderr has been removed since it was only
useful for `rake test:uncommitted` which was deprecated and removed.