Option hash not used in self#new

There is unused `options = {}` argument in `Sinatra.new` method:

```ruby
# Create a new Sinatra application. The block is evaluated in the new app's
# class scope.
def self.new(base = Base, options = {}, &block)
  base = Class.new(base)
  base.class_eval(&block) if block_given?
  base
end
```

So it can be dropped.
But this change is not really backwards-compatible with current Sinatra (somebody could just write `Sinatra.new(Sinatra::Base, {})` and it won't work after this commit), so it can be merged in 2.0, for example.