Choosing libraries for testing. (context, given)

[yujonglee]

Discussion in #56

There's few thing I want to share.

1. context is just aliases of describe.
   See source code. So I think the fact that this library is not maintained for 3 years doesn't really matters.

2. But, given2 is more complex library, and it's not maintaining these days too.
   So I find two alternative library. givens and bdd-lazy-var.

givens : similar interface with given2. Which is familiar to me and other RSpec-background-developers. Auther said it has advantages over given2and bdd-lazy-var. But I haven't used/heard of it so it needs some testing. It is also maintained by single author.

bdd-lazy-var : different interface with given2. Has more feature than given2, but they are not crucial.(in my opinion.) Good documentation. Many contributors. Updated(except bot) less than 1 year. It has built-in context aliases.

I'm not confident to choose one now. (jest-plugin-context + given2 or givens / bdd-lazy-var)
Need some testing and suggestions.