Update _nucleo-outline.scss

[eonward]

Fix relative paths to font assets
This targets issue #96

[einazare]

Hello there, @eonward37 ,

Thank you for your interest in working with our products and for sharing with us your fix.
To fix #96 you actually need to change '../fonts to '~assets/fonts.
If you wish, you can change this PR with the above fix, and point it to dev-master, and we'll integrate it in our next update.

Best,
Manu