v1.2.0

Added

• [BREAKING] Optional metadata parameter of type grpc.Metadata to the
  DgraphClientStub methods. options parameter moved to the third position
  to conform to the grpc package API.

  Methods affected - DgraphClient#alter, Txn#query, Txn#queryWithVars,
  Txn#mutate, Txn#commit and Txn#discard.

  To upgrade to this version, if using any of these methods with the options
  parameter, simply add a null argument before the options argument. For
  example, client.alter(options) becomes client.alter(null, options)