Remove Mac OS X build docs (#386)

Currently, Paddle on Mac OS X is not deliberate testing through the different versions of  Mac OS X and Clang.
When all these things that we've done, we will reopen Mac build docs.

doc/build/build_from_source.md

@@ -4,7 +4,6 @@ Installing from Sources
 * [1. Download and Setup](#download)
 * [2. Requirements](#requirements)
 * [3. Build on Ubuntu](#ubuntu)
-* [4. Build on Mac OS X](#mac)
 
 ## <span id="download">Download and Setup</span> 
 You can download PaddlePaddle from the [github source](https://github.com/gangliao/Paddle).
@@ -191,121 +190,3 @@ sudo pip install <path to install>/opt/paddle/share/wheels/*.whl
 # or just run 
 sudo paddle version
 ```
-
-## <span id="mac">Building on Mac OS X</span>
-
-### Prerequisites
-This guide is based on Mac OS X 10.11 (El Capitan). Note that if you are running an up to date version of OS X, 
-you will already have Python 2.7.10 and Numpy 1.8 installed.
-
-The best option is to use the package manager homebrew to handle installations and upgrades for you.
-To install [homebrew](http://brew.sh/), first open a terminal window (you can find Terminal in the Utilities folder in Applications), and issue the command:
-
-```bash
-# install brew
-/usr/bin/ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"
-# install pip
-easy_install pip
-```
-
-### Install Dependencies
-
-- **CPU Dependencies**
-
-  ```bash
-  # Install fundamental dependents 
-  brew install glog gflags cmake protobuf openblas
-
-  # Install google test on Mac OS X
-  # Download gtest 1.7.0
-  wget https://github.com/google/googletest/archive/release-1.7.0.tar.gz
-  tar -xzf googletest-release-1.7.0.tar.gz && cd googletest-release-1.7.0
-  # Build gtest
-  mkdir build && cd build && cmake .. && make
-  # Install gtest library
-  sudo cp -r ../include/gtest /usr/local/include/
-  sudo cp lib*.a /usr/local/lib
-  ```
-
-- **GPU Dependencies(optional)**
-
-    To build GPU version, you will need the following installed:
-
-        1. a CUDA-capable GPU
-        2. Mac OS X 10.11 or later
-        2. the Clang compiler and toolchain installed using Xcode
-        3. NVIDIA CUDA Toolkit (available at http://developer.nvidia.com/cuda-downloads)
-        4. NVIDIA cuDNN Library (availabel at https://developer.nvidia.com/cudnn)
-
-    The CUDA development environment relies on tight integration with the host development environment,
-    including the host compiler and C runtime libraries, and is therefore only supported on
-    distribution versions that have been qualified for this CUDA Toolkit release.
-        
-    1. After downloading cuDNN library, issue the following commands:
-
-        ```bash
-        sudo tar -xzf cudnn-7.5-osx-x64-v5.0-ga.tgz -C /usr/local
-        sudo chmod a+r /usr/local/cuda/include/cudnn.h /usr/local/cuda/lib/libcudnn*
-        ```
-    2. Then you need to set DYLD\_LIBRARY\_PATH, PATH environment variables in ~/.bashrc.
-
-        ```bash
-        export DYLD_LIBRARY_PATH=/usr/local/cuda/lib:$DYLD_LIBRARY_PATH
-        export PATH=/usr/local/cuda/bin:$PATH
-        ```
-
-### Build and Install
-
-As usual, the best option is to create build folder under paddle project directory.
-
-```bash
-mkdir build && cd build
-cmake ..
-```
-
-CMake first check PaddlePaddle's dependencies in system default path. After installing some optional
-libraries, corresponding build option will be set automatically (for instance, glog, gtest and gflags).
-If still not found, you can manually set it based on CMake error information from your screen.
-
-As a simple example, consider the following:
-
-- **Only CPU**
-
-  ```bash
-  cmake  .. -DWITH_GPU=OFF
-  ```
-- **GPU**
-
-  ```bash
-  cmake .. -DWITH_GPU=ON
-  ```
-
-- **GPU with doc and swig**
-
-  ```bash
-  cmake .. -DWITH_GPU=ON -DWITH_DOC=ON -DWITH_SWIG_PY=ON
-  ``` 
-
-Finally, you can build PaddlePaddle:
-
-```bash
-# you can add build option here, such as:    
-cmake .. -DWITH_GPU=ON -DCMAKE_INSTALL_PREFIX=<installation path>
-# please use sudo make install, if you want to install PaddlePaddle into the system
-make -j `sysctl -n hw.ncpu` && make install
-# set PaddlePaddle installation path in ~/.bashrc
-export PATH=<installation path>/bin:$PATH
-```
-**Note:**
-
-If you set `WITH_SWIG_PY=ON`, related python dependencies also need to be installed.
-Otherwise, PaddlePaddle will automatically install python dependencies
-at first time when user run paddle commands, such as `paddle version`, `paddle train`.
-It may require sudo privileges:
-
-```bash
-# you can run
-sudo pip install <path to install>/opt/paddle/share/wheels/*.whl
-# or just run 
-sudo paddle version
-```