Also:
- Changed base64 encoding of impersonator bearer tokens to use
`base64.StdEncoding` to make it easier for users to manually
create a token using the unix `base64` command
- Test the headers which are and are not passed through to the Kube API
by the impersonator more carefully in the unit tests
- More WIP on concierge_impersonation_proxy_test.go
Signed-off-by: Margo Crawford <margaretc@vmware.com>
