Error message for unsupported platform is not obviously from Turi Create

[znation]

The error message that prints out from pip install on an unsupported platform is helpful, but not obvious that it comes from Turi Create, so in a pip install -r requirements.txt type of scenario, the user may be at a loss as to how to proceed:

        ==================================================================================
        ERROR
        If you see this message, pip install did not find an available binary package
        for your system. Supported platforms are:
        * Linux x86_64 (including WSL on Windows 10).
        * macOS 10.12+ x86_64.
        * Python 2.7, 3.5, or 3.6.
        Other possible causes of this error are:
        * Outdated pip version (try `pip install -U pip`).
        ==================================================================================

Solution: we should probably mention somewhere obvious in this error message that it's Turi Create's issue. Pip doesn't really go out of its way to say that.