wakatime 2.1.6 (new formula)

Adding new formula for wakatime
It won't install when I use `Language::Python.setup_install "python", libexec` but it installs when I use `system "python", "setup.py", "install", "--prefix=#{prefix}"` with `bin.env_script_all_files(libexec+"bin", :PYTHONPATH => ENV["PYTHONPATH"])`.