The pserver need to have server index for saving model on the
distributed file system. The server index comes from etcd if etcd is
used, or user can manually specify them. So we need
pserver.NewService() to take index as an argument. Since index could
come from etcd, it would be strange if pserver takes an index as
argument, at the same time get the index from etcd. so we will need to
decouple pserver with etcd.

add eigen as cmake external project

Change the CpuMatrix::copyFrom and CpuVector::copyFrom with the strea…

Add `Variable::IsType`

Fix go get -d ./..

Change the CpuMatrix::copyFrom and CpuVector::copyFrom with the stream parameter to the synchronous interface.

add local recordio reader interface

FIX: Polish go library

scope design doc

Fix TravisCI with new building image.

Make user can check what type is in variable

fix MultiGradientMachine train and infer

Add convert to recordio function

Set ps_desired when pserver init

Add paddle/memory/README.md

Add recordio dependency

Move directory third_party into /build

Adding platform/must_check.h

__must_check is a macro mark of function return value. It let developer
must check the return value is legal or not.

Implement framework::Variable