Add a Dockerfile for the command-line interface (#1008)

* Add a Dockerfile for the command-line interface

* Check out tag 'stable' for building the CLI in Docker

this tag points to the latest release/tagged version.

* Update README.md for Docker as per review comments

* Capitalize Python

* Fix code snippet indention in the README for Docker

docker/README.md

@@ -10,12 +10,63 @@ Follow the general installation instructions
 * [OSX](https://docs.docker.com/installation/mac/): [docker toolbox](https://www.docker.com/toolbox)
 * [Ubuntu](https://docs.docker.com/installation/ubuntulinux/)
 
-## Running the Container
+## Using CLI Version of LightGBM via Docker
 
-Build the container, for python users:
+Build a Docker image with LightGBM CLI:
 
-    docker build -t lightgbm -f dockerfile-python .
+```
+mkdir lightgbm-docker
+cd lightgbm-docker
+wget https://raw.githubusercontent.com/Microsoft/LightGBM/master/docker/dockerfile-cli
+docker build -t lightgbm-cli -f dockerfile-cli .
+```
+
+where `lightgbm-cli` is the desired Docker image name.
+
+Run the CLI from the container:
+
+```
+docker run --rm -it \
+--volume $HOME/lgbm.conf:/lgbm.conf \
+--volume $HOME/model.txt:/model.txt \
+--volume $HOME/tmp:/out \
+lightgbm-cli \
+config=lgbm.conf
+```
+
+In the above example, three volumes are [mounted](https://docs.docker.com/engine/reference/commandline/run/#mount-volume--v-read-only)
+from the host machine to the Docker container:
+
+* `lgbm.conf` - task config, for example
+
+```
+app=multiclass
+num_class=3
+task=convert_model
+input_model=model.txt
+convert_model=/out/predict.cpp
+convert_model_language=cpp
+```
+
+* `model.txt` - an input file for the task, could be training data or, in this case, a pre-trained model.
+* `out` - a directory to store the output of the task, notice that `convert_model` in the task config is using it.
+
+`config=lgbm.conf` is a command-line argument passed to the `lightgbm` executable, more arguments can
+be passed if required.
+
+## Running the Python-package Сontainer
+
+Build the container, for Python users:
+
+```
+mkdir lightgbm-docker
+cd lightgbm-docker
+wget https://raw.githubusercontent.com/Microsoft/LightGBM/master/docker/dockerfile-python
+docker build -t lightgbm -f dockerfile-python .
+```
 
 After build finished, run the container:
 
-    docker run --rm -it lightgbm
+```
+docker run --rm -it lightgbm
+```

docker/dockerfile-cli

+FROM ubuntu:16.04
+
+RUN apt-get update && \
+    apt-get install -y cmake build-essential gcc g++ git && \
+    rm -rf /var/lib/apt/lists/*
+
+RUN git clone --recursive --branch stable https://github.com/Microsoft/LightGBM && \
+    mkdir LightGBM/build && \
+    cd LightGBM/build && \
+    cmake .. && \
+    make -j4 && \
+    make install && \
+    cd ../.. && \
+    rm -rf LightGBM 
+
+ENTRYPOINT ["lightgbm"]