export/risk:

Refactored the risk loss map export so that export to a file-like
object works properly and doesn't break because it's expecting a
file path. (So for example, this fixes the export if you want to
export to a StringIO object instead of the filesystem.)
Merge pull request #1262 from larsbutler/loss-map-export-minor-fix

Minor loss map export fix

[r=matley] [f=*trivial]