allow_unconfirmed_access_for set to nil means unconfirmed access for unlimited time

closes #2275
Merge pull request #2278 from plataformatec/issue-2275

allow_unconfirmed_access_for set to nil means unconfirmed access for unlimited time
Add #skip_confirmation_notification to Confirmable
Make use of warden's scoped serialization
Mention devise-encryptable requirement for anything but bcrypt.
Merge pull request #2296 from gregates/feature/skip_confirmation_notice!

Add #skip_confirmation_notification! to Confirmable
Merge pull request #2302 from islandr/master

Mention devise-encryptable requirement in initializer template
Changelog for #2296
Merge pull request #2305 from gregates/feature/skip_confirmation_notice!

Changelog for #2296
Merge pull request #2300 from fphilipe/scoped-serialization

Make use of warden's scoped serialization
Add Devise logo
Reduce logo dimentions
Crop the logo a bit more :bomb:
Update badges
Run image optimizer on the logo (i'm done)
updates source url to use https
Merge pull request #2308 from vfrride/patch-1

updates source url to use https
Improve documentation on sending delayed emails

There are a couple of gotchas in the existing documentation
about the `send_devise_notification` hook.

1.  The `after_commit` callback can be called multiple times
    so you should clear the array otherwise any additional
    invocations will trigger extra copies of the email.

2.  The `after_commit` callback is only called when a record
    is created or updated so you need to check for `new_record?`
    or `changed?` before adding it to `pending_notifications`
    otherwise it's okay to send it immediately.

The `new_record? || changed?` condition is necessary because
the latter isn't always true for new records, e.g:

    >> User.new.changed?
    => false

[ci skip]
Merge pull request #2311 from pixeltrix/improve-delayed-email-documentation

Improve documentation on sending delayed emails
Allow explicit configuration of http auth key

- Fix basic auth case in which authorized_keys is configured as hash
- Duplicate existing functionality when http_auth_key is not explicitly
  set