Performance improvements and new permissions

• Improved performance by no longer loading the list of all votes all the time
• Added new permission to see vote results before voting
• Added new permission to control the ability to change vote
• Security: when disabling "Allow people to see who voted", the API now no longer returns the details of the votes
• Security: the vote results are now hidden from the API until the user votes or has the new "see vote results" permission
• Fixed Pusher integration

This update is compatible with both Flarum beta 15 and 16.

To update, run:

composer require fof/polls:*
php flarum migrate
php flarum fof:polls:refresh

The last command might take longer to run on forums with a large number of polls.

If you use the Polls websocket messages as part of a custom integration, please give us feedback at #38