Proposal: Change the MesosStatusUpdateEvent taskStatus parameter to a String

I want to propose that the taskStatus parameter of MesosStatusUpdateEvent be changed to a String instead of an Int and its value to be changed to something more meaningful (i.e. TaskStatus.TaskState.name).

Currently, the taskStatus parameter is an Int with its value from getNumber which comes from the com.google.protobuf.ProtocolMessageEnum interface. This results in JSON events like the following:

 json
{
  "slaveId" : "20140428-140502-16842879-5050-4741-0",
  "taskId" : "app_11_0-1398700942222",
  "taskStatus" : 1,
  "appId" : "app_11",
  "host" : "vagrant.myshopify.io",
  "ports" : [ 31859 ],
  "eventType" : "status_update_event"
}

This change would make it look like this:

 json
{
  "slaveId" : "20140428-140502-16842879-5050-4741-0",
  "taskId" : "app_11_0-1398700942222",
  "taskStatus" : "TASK_RUNNING",
  "appId" : "app_11",
  "host" : "vagrant.myshopify.io",
  "ports" : [ 31859 ],
  "eventType" : "status_update_event"
}

I think this provides a more meaningful set of task states such as TASK_STAGING, TASK_STARTING, TASK_RUNNING, TASK_FINISHED, TASK_FAILED, TASK_KILLED and TASK_LOST.