lib: allow ReservationInfo.Type to be nil

[ajwerner]

This is to address incompatibility with Mesos 1.4 agent reservations as described in #340

[coveralls]

Coverage remained the same at 58.39% when pulling 8e9f780 on ajwerner:andrew/allow_reservation_info_type_to_be_nil into c488712 on mesos:master.

[jdef]

thanks for the PR! it looks like the gogo protobuf generation tools are out-of-sync w/ the version of the gogo tooling that's been vendored by the project. please see the travis config for how to install the right version of the tooling and then please re-generate the protos.

mesos-go/.travis.yml

Line 19 in c488712

- api/v1/vendor/github.com/gogo/protobuf/install-protobuf.sh

[coveralls]

Coverage remained the same at 58.39% when pulling 180ac5c on ajwerner:andrew/allow_reservation_info_type_to_be_nil into c488712 on mesos:master.

[ajwerner]

Should be good to go

[jdef]

thanks!