Source code change and compilation of xgboost-spark

In order to solve the problem that xgboost-spark only supports two classifications and does not support multiple classifications.

Source code changes refer to:

https://github.com/dmlc/xgboost/pull/2172/commits/ff73ff02c97006ec67b3d2e09f8afc503d4f0ff1

1. Install cmake

     Version 3.2 and above

     wget https://cmake.org/files/v3.6/cmake-3.6.2.tar.gz

     tar -xzvf cmake-3.6.2.tar.gz

     cd cmake-3.6.2

      ./bootstrap

     gmake

     gmake install

2, maven (abbreviation)

3、jvm-packages

     mvn clean package -DskipTests