Replace inline link with its text, a separator and its link

[tafel]

This PR adds the possibility to replace inline links with text and link.

It adds a new option separateLinksAndTexts which is null by default, and is the separator between text and link.

it('should replace inline link with text and link, with separator', function () {
  const string = 'some [inline link](http://www.test.net/).';
  const expected = 'some inline link: http://www.test.net/.';
  expect(removeMd(string, { separateLinksAndTexts: ': ' })).to.equal(expected);
});