Fix #1 by using pub key instead of cert

Sample output:

POSTing the following as a JWT bearer token:
eyAidHlwIjogIkpXVCIsICJhbGciOiAiUlMyNTYiIH0.eyAic3ViIjogImp3dC1iZWFyZXIt
Y2xpZW50IiwgImF1ZCI6IFsgImh0dHA6Ly9vcGVuYW0uZXhhbXBsZS5jb206ODA4OC9vcGVu
YW0iIF0sICJuYmYiOiAxNDE0NzQzMTQ3LCAiaXNzIjogImp3dC1iZWFyZXItY2xpZW50Iiwg
ImV4cCI6IDE0MTQ3NDM3NDcgfQ.M9VaGtiPXcT9zlHL4E41MTnx40yiZnQXuTCwnjwY56BPW
fvrR0siDGIVfxqbESSvJ2AWlS3qF1O4u12UYuK4xbtJhYy_8dNyq_nUD7paUGVyPCju-c4PM
G5KbedV-6ADXbKUv4NqPw1mzmwuMxsg0yqEjovHiM6hjHan9nO3io1r8FU6QSfu2-IuwanRY
TLajcIMzLatJfRMyPTBN0VytTmjdYnB0prol_xSYalNtQsmygvXrxEY7svm7DeCT13wPPCx9
aw3UVq_1STIGP2jDyAbe4cykWC5-iYUhacwLy1zbae36XXZ-8wrnPOuDypLkV_9aYajJxzj6
Ktn5t4d4Q

Response code: 200
{"expires_in":599,"token_type":"Bearer","access_token":"ba85c541-6a43-49
95-9eb6-6a4228a8c0c2"}