Update dev_setup_osx

[acknosyn]

Didn't realise at the time, Homebrew has now disabled the use of sudo with the brew command.

$ sudo brew install python
Error: Running Homebrew as root is extremely dangerous and no longer supported.
As Homebrew does not drop privileges on installation you would be giving all
build scripts full access to your system.

So I've updated the docs to remove sudo.

[coveralls]

Coverage remained the same at 52.314% when pulling a7d4cb1 on badraufran:feature/update_dev_setup_osx_brew_python into d3ecc0c on Netflix:develop.