Do not allow arrays without comma between values

[jeremyfa]

When playing with hscript, I noticed that the parser accepts this array without any comma as value separator:

var list = [ "carrot" 1234 null "potato" ];

I don't know if it is an oversight or if it's on purpose, but in my case I needed to forbid it, so here is a pull request of that change.

After the change, the same array needs to be declared like this:

var list = [ "carrot", 1234, null, "potato" ];

Feel free to merge or close that pull request, depending on whether this is intentional or not!

[ncannasse]

Thanks!