add read me for hadoop installation

Author: codeboyyong

hadoop-installtion/README.MD

@@ -0,0 +1,8 @@
+prerequest
+
+1) ssh to localhost without password
+
+	ssh-keygen -t dsa -P '' -f ~/.ssh/id_rsa 
+	cat ~/.ssh/id_rsa.pub >> ~/.ssh/authorized_keys 
+
+2) make sure JAVA_HOME exists in your shell