* Fix compiling error of gcc4.9.

* Refine the check of cxx compiler flags in api/CMakeLists.txt.

ImportError: /usr/local/lib/python2.7/dist-packages/py_paddle/_swig_paddle.so: cannot allocate memory in static TLS block

By shell command

```bash
sed -i 's#ifdef PADDLE_ONLY_CPU#ifndef PADDLE_WITH_GPU#g' `find ./paddle/ -name '*.h' -o -name '*.cc' -o -name '*.cpp' -o -name '*.c' -o -name '*.cu'`
sed -i 's#ifndef PADDLE_ONLY_CPU#ifdef PADDLE_WITH_GPU#g' `find ./paddle/ -name '*.h' -o -name '*.cc' -o -name '*.cpp' -o -name '*.c' -o -name '*.cu'`
```

* golang pserver optimizer config for user

* update

* update

* update

* update

* update by comments

* fix errors

* fix errors

* put everything in paddle wheel

* update

* update

* fix unitest

* with platform specs

Also remove operator bool in Error. The Error should be removed
later because it is not necessary for Paddle. We are now using Enforce
to handle error.

* using etcd as fault tolerant training

* update

* workable version, ft not tested

* small fix

* update

* remove TODO

Fix #2567

When using system python, "pip install" needs root previlege. Using virtualenv to avoid this.

cost is Argument, but argument does not have to be cost.