Support MongoDB session-wide write concern#3646

Merged

calvn merged 6 commits intomasterfrom mongodb-write-concern

Dec 5, 2017

+89-5

Commits on Nov 20, 2017

Initial work on write concern support, set for the lifetime of the session
calvn
committed

Commits on Dec 3, 2017

Merge branch 'master-oss' into mongodb-write-concern
calvn
committed

Commits on Dec 4, 2017

Commits on Dec 5, 2017

Remove writeConcern struct, move JSON unmarshal to Initialize
calvn
committed
Return error on empty mapping of write_concern into mgo.Safe struct
calvn
committed