update vts_hal_agent paths and add more setup instruction

Change-Id: I639a9a0141f9e9df56c417947f393629f5b01494
diff --git a/build-python.sh b/build-python.sh
index 1036cda..c953714 100755
--- a/build-python.sh
+++ b/build-python.sh
@@ -1,7 +1,9 @@
 #!/bin/bash
 
 # if "from future import standard_library" fails, please install future:
+#   $ sudo apt-get install python-dev
 #   $ sudo apt-get install python-pip
+#   $ sudo apt-get install python-virtualbox
 #   $ sudo pip install future
 #   $ sudo pip install futures
 #   $ sudo pip install enum
@@ -15,4 +17,4 @@
 # modify any import statements (to remove subdir path)
 protoc -I=proto --python_out=proto proto/AndroidSystemControlMessage.proto
 protoc -I=proto --python_out=proto proto/InterfaceSpecificationMessage.proto
-protoc -I=proto --python_out=proto proto/VtsReportMessage.proto
\ No newline at end of file
+protoc -I=proto --python_out=proto proto/VtsReportMessage.proto