eion/purple-hangouts

Merged in tofurky/purple-hangouts/image_history (pull request #24)

Add setting to control whether image history is fetched when opening group chats
// proto2 is required because we need to be able to serialize default values:
syntax = "proto2";
message GmailNotification {
optional string thread_id = 3;
//optional string previous_id = 4;
optional string id = 5;
repeated string labels = 6;
optional string subject = 7;
optional string snippet = 8;
optional string sender_name = 9;
optional string sender_email = 10;
//repeated unknown = 11;
}