Get all the headers we're going to need:

        1. Authorization
        2. Content-Type
        3. User-agent

        Note that the User-agent string contains the library name, the
        libary version, and the python version. This will help us track
        what people are using, and where we should concentrate our
        development efforts.

def _get_headers(self):
        """Get all the headers we're going to need:

        1. Authorization
        2. Content-Type
        3. User-agent

        Note that the User-agent string contains the library name, the
        libary version, and the python version. This will help us track
        what people are using, and where we should concentrate our
        development efforts."""

        user_agent = __api_lib_name__ + '/' + __version__ + '/' + \
            PYTHON_VERSION

        headers = {'User-Agent': user_agent,
                   'Content-Type': 'application/x-www-form-urlencoded'}
        if self.key:
            headers['Authorization'] = 'Bearer ' + self.key
        return headers