Update to pug-lexer@4 & co, and make unit tests pass again

[lehni]

Relates to #148, but makes unit tests pass again by adjusting code for internal pug changes:

• Lexer returns lines / columns in a different format, with sometimes slightly different values than before
• This is now valid syntax in pug 2:

  div
  |
  div

[lehni]

The tests pass on Node 6, but fail on the older versions because the dependency docco uses the spread operator. That's not an error in this PR, but probably means that the supported and tested Node versions should change.

[adrienverge]

Hi @lehni,

Is there any backward-incompatibility? Can it break some projects build/lint chain?

[lehni]

@adrienverge well it passes the full test suite, so I don't think so. The only thing that's different that I found was that Pug 2 doesn't consider this invalid markup anymore:

div
|
div

And it shouldn't be:

<div></div><div></div>

just like this:

div
| text
div

now produces:

<div></div>text<div></div>

[ezhlobo]

@adrienverge could you please mention people whose review is required here? Will be nice to have it merged :).

[adrienverge]

@ezhlobo given the lack of activity here, I'd say that any member's approval will be enough.

It seems like we are 3 to think it's a good changes, so let's merge.

[lehni]

Great, thanks!