'Initialize the Jinja2 Environment object while loading extensions.
Does the following:
1. Establishes default_extensions (currently just a Time feature)
2. Reads extensions set in the cookiecutter.json _extensions key.
3. Attempts to load the extensions. Provides useful error if fails.'

def __init__(self, **kwargs):

    context = kwargs.pop('context', {})
    default_extensions = ['cookiecutter.extensions.JsonifyExtension', 'jinja2_time.TimeExtension']
    extensions = (default_extensions + self._read_extensions(context))
    try:
        super(ExtensionLoaderMixin, self).__init__(extensions=extensions, **kwargs)
    except ImportError as err:
        raise UnknownExtension('Unable    to    load    extension:    {}'.format(err))
