Email in generated certificate looks incorrectly encoded

```
$ ./venv/bin/python demo-client.py stefan@arentz.nl cheesecheese login

...

HAWK_POST https://api-accounts.dev.lcip.org/v1/certificate/sign
cert: eyJhbGciOiJSUzI1NiJ9.eyJwdWJsaWMta2V5Ijp7ImFsZ29yaXRobSI6IlJTIiwibiI6IjEzNDA3ODA3OTI5OTQyNTk3MDk5NTc0MDI0OTk4MjA1ODQ2MTI3NDc5MzY1ODIwNTkyMzkzMzc3NzIzNTYxNDQzNzIxNzY0MDMwMDczNTQ2OTc2ODAxODc0Mjk4MTY2OTAzNDI3NjkwMDMxODU4MTg2NDg2MDUwODUzNzUzODgyODExOTQ2NTY5OTQ2NDMzNjQ5MDA2MDg0MDk2IiwiZSI6IjIifSwicHJpbmNpcGFsIjp7ImVtYWlsIjoibHzvv71uR--_vUDvv73vv70h77-9XCLvv73vv71fXHUwMDA1QGFwaS1hY2NvdW50cy5kZXYubGNpcC5vcmcifSwiaWF0IjoxMzg2NjQ0MjUyOTgxLCJleHAiOjEzODY3MzA2NTI5ODEsImlzcyI6ImFwaS1hY2NvdW50cy5kZXYubGNpcC5vcmcifQ.IpXQBODvE89gv70yqU2MHZPHCbOSpG-DyT2iKRylet0NWL9IspNhHM28DwRXH4pjsyj1a_es194mty7K8YuT3llIFO_uvkhPbS9EKfpXgEC9YB2y-bJMG1SrRATDKBbBvWQw8dHMKaXnbxBcy8SxPm3w4ze-cjlFgSUNUzsVi1FLQK30gxVSJY0R1dy1O1XP7bIXjJ-qdCPXtZoAXcCvW-ZLEnmqoaOPFEFnu_RvcC-qq1wgNj2SXH2I_yctJMCjuGMKcweu7dYYEs6BWRdEadsR85Ke8mxupAxlZeHrUS6NP4axspof8gVNSN5fGbtn9o4xrfKhl5VRHbygrTsjEg

header: {u'alg': u'RS256'}
payload: {u'iss': u'api-accounts.dev.lcip.org', u'iat': 1386644252981,
u'public-key': {u'e': u'2', u'algorithm': u'RS', u'n': u'13407807929942597099574024998205846127479365820592393377723561443721764030073546976801874298166903427690031858186486050853753882811946569946433649006084096'},
u'exp': 1386730652981,
u'principal': {
  u'email': u'l|\ufffdnG\ufffd@\ufffd\ufffd!\ufffd"\ufffd\ufffd_\x05@api-accounts.dev.lcip.org'}}
```