* added relay quick start

* added relay/using_external_lib.py

* update using_external_lib

* Update using_external_lib.py

* update tvm/make/config.mk -> cmake/config.cmake

* Fixed: result mismatched when lowering relay with cudnn support at opt level 2

* setting opt_level=2 and out_channels=16 for consistency of original tutorial

* Fixed some typos