Powerline patched font not working on Terminal.app
Let me suggest you to install Input Mono font, comes with full support to powerline. 

In order the following to work, Input Mono font must be version 1.1. You can check the font version by going to Font Book → View → Show Font Info, and look at the version number.

With Terminal.app works out of the box. Just select the font and you are ready.

With iTerm2, you have to modify a couple of things:


Go to Preferences → Profiles → Text and uncheck `Use a different font for non-ASCII text.
Just above, click on Change Font and select Input Mono. Additionally you have to change Character Spacing → Vertical to 110%. Seems that Terminal and iTerm2 render character spacing in a different way.