Update _load_azure_token

[rabidang3ls]

_load_azure_token would fail if the "expires-on" field was not comprised of digits. The field isn't guaranteed to be digits, so this updates the code to also accept the date format `%Y-%m-%d %H:%M:%S.%f

FIx for #84

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[bitsofinfo]

@rabidang3ls whats the status of this? really need it! thank you

[rabidang3ls]

@bitsofinfo I don't know the project well enough to understand their travis-ci output. Not sure what fails, but I haven't had any issues with it. Looks like #141 passed all checks and should be implementing the same fix.