added xgboost in linux build

build_linux_dependencies.sh

 #!/bin/sh
 
-cd alphamind/pfopt
+cd xgboost
+git submodule init
+git submodule update
 
-./build_linux.sh
+make -j4
+cd python-package
+python setup.py install
+
+if [ $? -ne 0 ] ; then
+    cd ../..
+    exit 1
+fi
+
+cd ../..
 
+cd alphamind/pfopt
+./build_linux.sh
 if [ $? -ne 0 ] ; then
     cd ../..
     exit 1