1.6.0-beta1

WARNING: this (pre-)release (long time due) makes a step forward in PHP
compatibility, leaving behind obsolete versions. While yii2-usuario should
still work without issues on 5.6, from now on testing and development will
look forward and maintain only >=7.4 versions.

There's also a security issue for 2FA tokens: settings/two-factor route
wasn't checking for the currently logged in user, so any authenticated account
could access to all user's 2FA root code. If you cannot upgrade, check
24d5d5744fe0.

There's also a change in flash messages handling, please see #391 for details.

For a full list of changes, see CHANGELOG.md.

People are encouraged to update translation files.