Problems installing powerline fonts on macOS 10.12
Fixed. It was me just being dumb.
Everything was properly installed and working but I realized that iTerm2 and the stock Terminal app were set to use a different kind of font so that's why it wasn't displaying some characters.
Going into iTerm2's settings and manually overriding the fonts fixed the issue.
I had this issue today, basically to enable the Powerline fonts from iTerm2, just go over to Preferences > Profiles > Text and check the box for "Use built-in Powerline glyphs".