Travis: Drop custom caching and switch to node.js 8.

[XhmikosR]

Fixes #310

[XhmikosR]

@cvrebert: it appears coveralls fails, not due to this patch, though.

And the build isn't marked as failed, not sure if that's intentional.

[XhmikosR]

Looking into the coveralls issue, it seems it's due to fishbar/jscoverage#35

The potential fix might be something as simple as

require("coffee-script/register")

Should we fork jscoverage or look for alternatives?

So this leaves us the build being marked as successful.

[cvrebert]

Should we fork jscoverage or look for alternatives?

I would warmly welcome a patch to switch to Istanbul. I'm open to proposals for other alternative tools too.
But it seems like the easiest fix would be to just add a devdependency on coffeescript and stick with jscoverage, so I'd also accept a patch for that.

[cvrebert]

Can't we just refer to the Gemfiles from our git clone of Bootstrap?

[XhmikosR]

That I don't know,

[cvrebert]

Should just be a matter of moving the clone into the install steps and adding a couple cp commands after the clone.

[XhmikosR]

It should be doable, yes. Feel free to push here if you want.

[cvrebert]

Okay, added to my todo list

[XhmikosR]

I might give it a go if I have time too, but I can't promise anything.

[XhmikosR]

But it seems like the easiest fix would be to just add a devdependency on coffeescript and stick with jscoverage, so I'd also accept a patch for that.

Nope, I tried that but still fails.

[cvrebert]

not due to this patch, though.

Ah. Then open a new issue and we'll ignore the failure for now.

[XhmikosR]

@Johann-S: I totally forgot I had made this. I'll test it out.