Add multiroot CA.

[kisom]

This is a CA that supports multiple signature keys.

[coveralls]

Coverage increased (+0.97%) to 48.62% when pulling beee598 on kyle/multiroot into 534b084 on master.

[coveralls]

Coverage increased (+0.97%) to 48.62% when pulling beee598 on kyle/multiroot into 534b084 on master.

[coveralls]

Coverage increased (+0.9%) to 48.55% when pulling cdb120e on kyle/multiroot into 534b084 on master.

[coveralls]

Coverage increased (+0.68%) to 48.34% when pulling 564302f on kyle/multiroot into 534b084 on master.

[coveralls]

Coverage increased (+1.58%) to 49.24% when pulling 5698427 on kyle/multiroot into 534b084 on master.

[lziest]

LGTM