Add definitions

[jackiekazil]

The federal government says that they give 12 weeks "paid" sick leave, but it is not equal to 12 weeks a company in the list probably gives. (here is an explanation: http://www.federaltimes.com/story/government/management/compensation/2015/01/15/paid-family-leave/21802251/ -- the thing to note is that is it not paid as much as it is an advancement of sick time and vacation (after you have burned through all of you vacation and sick time)

Thoughts --

1. Add a specific definition of what "paid" parental leaves means.
2. Add a way to describe what is offered in the case that it does not meet the definition of parental leave. (I can see this one mucking up the dataset.)

I willing to submit a pull request, but thought it might need some discussion first.
Discuss.