Fix nesting markup in links

[kristijanhusak]

Related PR: #431

[kristijanhusak]

@gzagatti can you give this PR a test and see if it fixes the issues? It removes some of the code and should fix nesting of the markup and links, at least from what I saw how Emacs behaves.

[kristijanhusak]

Ok I figured out this breaks all the LateX stuff that you did, so I need to reconsider this.

[kristijanhusak]

I think I covered everything. There are some edge cases where it might not behave exactly as Emacs, but it generally doesn't look like valid markup in there also.

[gzagatti]

The code does not seem to tackle cases like:

This is =a *1  b= and *ab cd* foo

Where =a *1 b= should be verbatim and *ab cd* should be bold. We might need to handle orphans like I did PR #431. I could try to bring that logic to this branch. I will just wait for your feedback on my comments in there.