Add non-production environment names to web UI title

Something like this would be pretty helpful for us since we often have Sidekiq web UI tabs open for local, staging, production, etc. all at once.

(Also, I wasn't sure if non-Rails Ruby apps are supported, but obviously more frameworks could be supported pretty easily.)
Looks good, you're only missing `Sidekiq.options[:environment]` which will be set if the user uses the `-e` CLI flag: `sidekiq -e staging` so this line should be:

```ruby
environment = Sidekiq.options[:environment] || ENV['RAILS_ENV'] || ENV['RACK_ENV'] || 'development'
```