harvesting: bug with remote funder loading

[krzysztof]

On some systems, loading full fundref dataset using requests raises: UnicodeEncodeError: 'ascii' codec can't encode character u'\u2019' in position 1551758: ordinal not in range(128)

This unit tests reproduces it:

def test_full_remote_fundref_loader(app):
    """Test the remote loadef for the FundRef dataset."""
    with app.app_context():
        frl = RemoteFundRefLoader()
        json_dataset = list(frl.iter_funders())
        assert len(json_dataset) == 5

But also short snipplet like:

import requests
r = requests.get('http://dx.doi.org/10.13039/fundref_registry')
with open('tmp.xml', 'w') as f:
   f.write(r.text)