Use environmental variable for VS_INSTALL_PATH.

Author: Prcuvu

env.bat.template

@@ -3,4 +3,4 @@ set RIME_ROOT=%CD%
 set BOOST_ROOT=\code\boost_1_60_0
 set CMAKE_INSTALL_PATH=C:\Program Files (x86)\CMake
 set GIT_INSTALL_PATH=C:\Program Files (x86)\Git
-set VS_INSTALL_PATH=C:\Program Files (x86)\Microsoft Visual Studio 14.0
+set VS_INSTALL_PATH=%VS140COMNTOOLS%\..\..