Prefer Time.now over Time.new

The documentation says now is an alias for new. I believe Time.now more
clearly conveys that it uses the current time, whereas Time.new does not
convey the current time vs. an arbitrary, empty time object.

GitHub search indicates that Time.now is far more popular:

* Time.now has [376,997 code results](https://github.com/search?l=ruby&q=time.now&source=c&type=Code)
* Time.new has [18,858 code results](https://github.com/search?l=ruby&q=time.new&source=c&type=Code)

The ratio of now:new is approximately 20:1.