Update password length validation to 72 characters max

BCrypt has a limit of 72 characters for the password. Anything beyond 72
characters is truncated. This commit updates the validation to limit
passwords to less than 72 characters, keeping within the limitation.
Yield the resource in RegistrationsController#new
Merge pull request #3320 from deivid-rodriguez/yield_the_resource_in_registrations_controller_new_action

Yield the resource in RegistrationsController#new
Merge pull request #3319 from lleger/lleger-fix-password-length

Update password length validation to 72 characters max
Update CHANGELOG [ci skip]
Update Gemfiles.
Option to validate upon #confirm!

Allow to ensure valid upon confirming.
We might want to consider confirmation status in validations. For example, maybe we want to require certain fields upon confirmation, but not at registration.
Use the new build env on Travis

- use the new build env on Travis (sudo: false) (docs coming soon)
  faster vms, more cpu, more ram, faster vm boot time
- remove the custom caching for now as the new setup has a far better network
- add rails-head to the gemfile list as it wasn't there

caching is generally not recommended for libs like Devise as you want to test against the latest gem versions. Caching will use the min requirements available on the system instead of retrieving the latest.

On that note, it is also recommended to remove the Gemfile.lock from the repo. For now I have just 'rm'd it before 'bundle install'
there is no rails-head Gemfile
remove the relevant Gemfile.lock
use built in travis caching

make sure bundle update is run so that the latest gems are used
Made ensure valid a named param for confirm!, and added a test.
Use args hash instead of named parameters for confirm!
Merge pull request #3324 from timscott/patch-1

Option to validate upon #confirm!
Ability to load modules in specific order

Allow modules to be inserted at set positions
Update devise.rb
Merge pull request #3325 from joshk/patch-2

Use the new build env on Travis
Merge pull request #3328 from stephenbaldwin/master

Ability to load modules in specific order
Remove old references to removed remember_across_browsers option
Merge pull request #3333 from rosenfeld/master

Remove old references to removed remember_across_browsers option