Update configuration docs about @jest-environment (#3281)
Update configuration docs about @jest-environment (#3281)

* Update configuration docs about @jest-environment

The @jest-environment docblock is a feature that's coming in Jest version 20.0.0.
This commit adds this information to the documentation.

* Fix formatting in docs

cpojer/jest,mpontus/jest,skovhus/jest,ide/jest,bookman25/jest,cpojer/jest,ide/jest,cpojer/jest,bookman25/jest,facebook/jest,facebook/jest,skovhus/jest,mpontus/jest,ide/jest,bookman25/jest,facebook/jest,mpontus/jest,skovhus/jest