Twenty Fourteen: Remove unused font weights to reduce page load

[iamtakashi]

In The theme, some weights for Lato: thin (100) and thin italic (100 italic) are not used and they are too thin to be displayed well anyway, we can remove those to save some impact on page load. Not sure how much exactly it would be, it's probably very small but I still think it's worthwhile.

[johnbillion]

See also the current discussion on bundling Open Sans: ​http://make.wordpress.org/core/2013/11/11/open-sans-bundling-vs-linking/

[lancewillett]

In 26099:

Twenty Fourteen: don't load unused font weights. Props iamtakashi, fixes #25922.