TTF: regen. from OTFs

The side effect of this is that TTFs are significantly bigger, e.g. 490Kb vs. 228Kb for the Roman weight when generating from SFD (I didn't see any visual difference vs. the old TTF, I mean besides the modified metrics).

Below are visual comparisons with Firefox 29 under Windows 7 DirectWrite rendering.

OTF:

![otf](https://cloud.githubusercontent.com/assets/1250894/2973081/674fd6dc-db7a-11e3-988c-9fcb6e03b8b1.PNG)

TTF:

![ttf](https://cloud.githubusercontent.com/assets/1250894/2973085/6f185de4-db7a-11e3-9ff7-b791c248d9d1.PNG)

For reference, the old TTF:

![old-ttf](https://cloud.githubusercontent.com/assets/1250894/2973089/7b9fea28-db7a-11e3-9810-507a0950cc27.PNG)

cc @rainerschuhsler, closes #3.

r? @skosch