Add a version incongruity warning.

[madroneropaulo]

It would be handy to warn people about some incongruities between the handbook information and the different typescript versions, like "this handbook refers to typescript 1.5, for newer versions, please seee latest TypeScript Language Specification." Specially if the handbook updates are not planned to be released soon. Issue related to #139

[mhegazy]

The handbook has been updated, see https://blogs.msdn.microsoft.com/typescript/2016/03/24/new-typescript-website/. moving forward, we should be updating the handbook along with the release.