Ruby 2.4.0 unifies Fixnum and Bignum into Integer.

https://bugs.ruby-lang.org/issues/12005

Fix following deprecated warnings in Ruby 2.4.0-preview3.

- `warning: constant ::Fixnum is deprecated`
- `warning: constant ::Bignum is deprecated`

use existence of 'Rails::Application' as indicator of Rails App instead of 'Rails', as many Ruby applications are using railties such as generators outside Rails

* add(annotate_models_spec): test coverage
* change(annotate_models#get_foreign_key_info): elide auto-generated fk names

Closes #404.

* Correct 'comas' to 'commas' in README

* Provide :hide_default_column_types option to make hiding of default configurable

* Use `NO_DEFAULT_COL_TYPES` as default when the `hide_default_column_types` option is not provided

* add option to exclude STI subclasses from annotation

Fix configuration in rails README link

Annotate should reset the cached information about columns

fix so that the wrapper-opening does not gets duplicated

Fix bundle in windows platform.

Allow rake 11 in annotate.gemspec

Annotate on_delete/on_update foreign key constraints

Add unit tests for classified sort option

Allow classified sorting without an ID column

Fix fatal error when using `annotate` with ActiveRecord 4.1

The fatal error was introduced with commit fc31d85. The method
`supports_foreign_keys?` is only available on ActiveRecord versions
>= 4.2.

Fixes issue 316.

Fix rubocop problems due to version change

 - Replace SpaceAroundKeyword with SpaceAfterControlKeyword
 - Use an explicit rubocop version to avoid breakages during PRs

Don't leave wrapper when removing annotations

Annotate should reset the cached information about columns because Annotate may output old information if we load ActiveRecord::Base class in migration files.

For example, if we have a following migration file and execute 'rake db:migrate', Annote does not output the default value and a not null constraint of the `some_value` column.

```ruby
class CreatePosts < ActiveRecord::Migration
  def change
    create_table :posts do |t|
      t.integer :some_value
    end

    # add a not null constraint to the some_value column

    # should update some_value with not null values
    # because records might exist which have null value in the some_value column

    Post.update_all(some_value: 1)

    change_column_null(:posts, :some_value, false)
    change_column_default(:posts, :some_value, 1)
  end
end
```

This commit fixes the above issue.

Added coveralls.