bobthefish: print the bold glyph font.

related to this old discussion in #66

I just have to download https://github.com/Lokaltog/powerline/blob/develop/font/PowerlineSymbols.otf into ~/.fonts

to get the same beautiful screenshot. (with some visible artifact)

With this fix, following the README
using the font in [Lokaltog/powerline-fonts](https://github.com/Lokaltog/powerline-fonts)
I noticed that the font wasn't the same between normal and bold
![powerline_font](https://cloud.githubusercontent.com/assets/3978761/3563296/20584566-0a2d-11e4-9c68-ac71ccb02c5f.png)


This branch will print the glyph using set_color --bold


I think this might be an interesting fix, so I just propose this merge request.