Install md (#2512)

* Add INSTALL.md.

PaddleCV/object_detection/docs/INSTALL.md

+# Installing PaddleDetection
+
+---
+## Table of Contents
+
+- [Introduction](#introduction)
+- [PaddlePaddle](#paddlepaddle)
+- [Other Dependencies](#other-dependencies)
+- [PaddleDetection](#paddle-detection)
+- [Datasets](#datasets)
+
+
+## Introduction
+
+This document covers how to install PaddleDetection, its dependencies (including PaddlePaddle), and COCO and PASCAL VOC dataset.
+
+For general information about PaddleDetection, please see [README.md](../README.md).
+
+
+## PaddlePaddle
+
+Running PaddleDetection requires PaddelPaddle Fluid v.1.5 and later. please follow the installation instructions in [installation document](http://www.paddlepaddle.org/documentation/docs/en/1.4/beginners_guide/install/index_en.html).
+
+Please make sure your PaddlePaddle installation was sucessful and the version of your PaddlePaddle is not lower than the version required. You can check PaddlePaddle installation with following commands.
+
+```
+# To check if PaddlePaddle installation was sucessful
+python -c "from paddle.fluid import fluid; fluid.install_check.run_check()"
+
+# To print PaddlePaddle version
+python -c "import paddle; print(paddle.__version__)"
+```
+
+### Requirements:
+
+- Python2 or Python3
+- CUDA >= 8.0
+- cuDNN >= 7.0
+- nccl >= 2.1.2
+
+
+## Other Dependencies
+
+**Install the [COCO-API](https://github.com/cocodataset/cocoapi):**
+
+To train the model, COCO-API is needed. Installation is as follows:
+
+    git clone https://github.com/cocodataset/cocoapi.git
+    cd cocoapi/PythonAPI
+    # if cython is not installed
+    pip install Cython
+    # Install into global site-packages
+    make install
+    # Alternatively, if you do not have permissions or prefer
+    # not to install the COCO API into global site-packages
+    python setup.py install --user
+
+
+## PaddleDetection
+
+**Clone Paddle models repository:**
+
+You can clone Paddle models and change directory to PaddleDetection module with folloing commands:
+
+```
+cd <path/to/clone/models>
+git clone https://github.com/PaddlePaddle/models
+cd models/PaddleCV/object_detection
+```
+
+**Install python module requirements:**
+
+Other python module requirements is set in [requirements.txt](./requirements.txt), you can install these requirements with folloing command:
+
+```
+pip install -r requirements.txt
+```
+
+**Check PaddleDetection architectures tests pass:**
+
+```
+export PYTHONPATH=$PYTHONPATH:.
+python ppdet/modeling/tests/test_architectures.py
+```
+
+
+## Datasets
+
+PaddleDetection support train/eval/infer models with dataset [MSCOCO](http://cocodataset.org) and [PASCAL VOC](http://host.robots.ox.ac.uk/pascal/VOC/), you can set up dataset as follows.
+
+**Create symlinks for datasets:**
+
+Dataset default path in PaddleDetection config files is `data/coco` and `data/voc`, you can set symlinks for your COCO/COCO-like or VOC/VOC-like datasets with following commands:
+
+```
+ln -sf <path/to/coco> $PaddleDetection/data/coco
+ln -sf <path/to/voc> $PaddleDetection/data/voc
+```
+
+If you do not have datasets locally, you can download dataset as follows:
+
+- MSCOCO-2017
+
+```
+# download
+wget http://images.cocodataset.org/zips/train2017.zip
+wget http://images.cocodataset.org/zips/val2017.zip
+wget http://images.cocodataset.org/annotations/annotations_trainval2017.zip
+
+# decompress
+unzip train2017.zip
+unzip val2017.zip
+unzip annotations_trainval2017.zip
+```
+
+- VOC2012
+
+```
+# download
+wget http://host.robots.ox.ac.uk/pascal/VOC/voc2012/VOCtrainval_11-May-2012.tar
+
+# decompress
+tar -xf VOCtrainval_11-May-2012.tar
+```
+
+**Auto download datasets:**
+
+If you set up models while `data/coc` and `data/voc` is not found, PaddleDetection will automaticaly download them from [MSCOCO-2017](http://images.cocodataset.org) and [VOC2012](http://host.robots.ox.ac.uk/pascal/VOC), the decompressed datasets will be places in `~/.cache/paddle/dataset/` and can be discovered automaticaly in the next setting up time.
+
+
+**NOTE:** For further informations on the datasets, please see [DATASET.md](../ppdet/data/README.md)
+