Token auth

[tegataiprime]

Adding an option for token based authentication.

e.g.

curl -H "Authorization: token=$(dcos config show core.dcos_acs_token)" http://m1:8080/v2/apps/{id}

[coveralls]

Coverage decreased (-2.3%) to 66.5% when pulling e81085a on tegataiprime:tokenAuth into 5a25be8 on aatarasoff:master.