Fixed Time.new with arguments in Ruby 1.9.2+ 

The Ruby 1.9.2+ Time constructor can take arguments, which causes an ArgumentError once the aliasing happens:

```
1.9.3p194 :003 >   ::Time.new(2005, 11, 10, 12, 0, 2, 0)
 => 2005-11-10 12:00:02 +0000 
1.9.3p194 :004 > require 'time_warp'
 => true 
1.9.3p194 :005 > ::Time.new(2005, 11, 10, 12, 0, 2, 0)
ArgumentError: wrong number of arguments (7 for 0)
	from /Users/bortega/.rvm/gems/ruby-1.9.3-p194-i386/gems/time-warp-1.0.13/lib/core_ext/time.rb:12:in `now'
	from (irb):5
	from /Users/bortega/.rvm/rubies/ruby-1.9.3-p194-i386/bin/irb:16:in `<main>'