Add page with tips for programmers coming from other languages

Lately there has been a range of questions on the forum for things that are already explained somewhere in the docuementation/blogs/release notes. The purpose of this pull is to create a quick summary for people coming from a specific language.

This pull request is based on [this discussion](https://groups.google.com/d/topic/elm-discuss/lqo-AeYvgPM/discussion) and for now contains points for Haskell and JS/HTML/CSS.

The intention is to keep it short (bullet form) and link to relevant documentation.

The page is not intended to be a tutorial or contain lengthy explanations or take focus away from the main documentation.