Make markdown links consistent on cursor exits

Make the versions of link with and without * behave alike:

-   don't set the 0 location so that the cursor exits.
    Having a 0 in the title is bad because titles are short.

-   either open a new line at end for both, or for neither

    The only case where the newline is certain is for link definitions.
> I don't clearly understand what you mean, but I'm sure it's something I have to learn about! I'll try to understand.

To clarify: Vim does not inform plugins about the actions the user took, only about Cursor movement. Since UltiSnips needs to understand if you added/removed/changed text (for example to mirror the text correctly) it uses a bunch of heuristics that are based on the diff between the last snippet text and the one after a cursor moved. 

That means that UltiSnips is diffing parts of your buffer on each keystroke given that a snippet is active (a snippet is going inactive when you leave its bounds or when you reach the 0 tabstop). Diffing is very expensive (O(chars^2)) so we want to do it as little as possible - that is why placing the 0 tabstop is very important.