adds a preamble to the guides generator, documents what it does and the environment variables it supports

Raise a StatementInvalid error when trying to build a condition with hash keys that do not correspond to columns.

Refactored url_for in AV to have its own instances of the helpers instead of proxying back to the controller. This potentially allows for more standalone usage of AV. It also kicked up a lot of dust in the tests, which were mocking out controllers to get this behavior. By moving it to the view, it made a lot of the tests more standalone (a win) 

Make the query built by has_many ...., :dependent => :____ lazy since all the information is not really available yet.

Signed-off-by: Nwycats <wycats@gmail.com>

guides: warn about edge guides at the top of the home preamble, and mention that only for edge guides, stable guides need no warning

Signed-off-by: NJosé Valim <jose.valim@gmail.com>

Maintain the usage of :as consistent in the router. Whenever it's supplied, it changes the NAMED ROUTE. If you want to change the PATH, use :path instead. Example: resources :projects, :path => 'projetos'

Signed-off-by: Nwycats <wycats@gmail.com>

Restore changed_attributes method in ActiveModel::Dirty and loosen expectation on including class' initialize method.

[#4308 state:committed]
Signed-off-by: NJeremy Kemper <jeremy@bitsweat.net>

Slightly less annoying check for acceptable mime_types. This allows Accept: application/json, application/jsonp (and the like), but still blacklists browsers. Essentially, we use normal content negotiation unless you include */* in your list, in which case we assume you're a browser and send HTML [#3541 state:resolved]