"checker" is the name being used everywhere.

This sucks, but otherwise I get occasional Fs on Mac OS X.

Mac OS X tries by all means to hide that /var is /private/var, and that is
what FSEvents reports back.

In particular files are no longer created in the current working directory,
but in a temporary folder.

This commit also bases everything on Pathname internally.

3.0.3 has a bug in OS X.

This is the implementation of the file update checker written
by Puneet Agarwal for GSoC 2015 (except for the tiny version
of the listen gem, which was 3.0.2 in the original patch).

Puneet's branch became too out of sync with upstream. This is
the final work in one single clean commit.

Credit goes in the first line using a convention understood
by the contrib app.

fix method name typo [ci skip]

ActiveJob docs text fix. [ci skip]

Allow `host` option in javscript and css helpers

dry up increment/decrement

fix application_controller require_dependency path generated by api scaffold generator

Improve support for non Active Record objects on `validates_associated`

Now both `javascript_include_tag` and `stylesheet_tag` can accept `host` option
to provide custom host for the asset

Skipping `marked_for_destruction?` when the associated object does not responds
to it make easier to validate virtual associations built on top of Active Model
objects and/or serialized objects that implement a `valid?` instance method.

In the app generator, regardless of the namespace, it is adapted to read the same `application_controller.rb`,
modified to api generator also be the same behavior.

ref 686966a1, 06ac63b4

Fix Unnecessary variable assignment /associations/builder/belongs_to.rb#add_destroy_callbacks

There is no need to to assign reflection name to a variable, because it's called once.

Parameterize with options to preserve the case of string