Set contentType to 'image/svg+xml' when format is 'svg'
set format to html for .svg requests

This is because we use the format variable to access the correct panel
of the bin, which means our check for html must now also check the mime
type
use req.bin.svg instead of format
add svg to route regex
Merge pull request #1467 from jsbin/feature/svg-mime

Feature/svg mime