Sapper: non-page route should not set content-type

[samhatchett]

https://github.com/sveltejs/sapper/blob/master/lib/index.js#L200

... does not check for route type. by setting a default type of text/html, Sapper ends up overriding useful auto-checking of mime types by express, especially for download content.

[EmilTholin]

Hi @samhatchett! That's a very good point. That line of code you linked should possible be moved here instead?

[samhatchett]

looks right to me. mind if I open a PR?

[EmilTholin]

I think that would make Rich a very happy man.

[jacobmischka]

I think a similar change should also be made here. This forcing of js content-type is I believe the only thing stopping custom assets by webpack from working (extract-text-plugin for css or file-loader for font assets, for examples).

[samhatchett]

primary issue fixed via #111 - similar change from @jacobmischka not yet addressed.

[Rich-Harris]

The core issue here is fixed so I'll close this, but I've opened a new ticket (#116) for the related issue @jacobmischka found