Add time_sugar, a lightweight alternative to activesupport time stuff

Hi again, everybody!

Before I start I want to say that I'm ok if you reject this PR (it would be the first one, haha).

[time_sugar](https://github.com/patriciomacadden/time_sugar) adds some syntactic sugar for handling time, like:

```ruby
>> 1.week.ago
=> 2014-03-03 19:49:44 -0300
>> 2.days.ago
=> 2014-03-08 19:49:47 -0300
>> 1.week.from_now
=> 2014-03-17 19:49:51 -0300
>> 2.days.from_now
=> 2014-03-12 19:49:54 -0300
```

without the need of active support. I know there are a few other similar libraries, but this is smaller and does only one thing.

PS: this time I reformatted the whole json!