update cmakelist file to support new NDK version 

use miniSDKVersion 19 

releasev2.1.3 

modify implementation to api in library 

add -lz 

support x86 

update OpenCv to v4.1.0 

update readme 

release 1.2.4 1. support arm64-v8a 2. compile and target sdk version 28

release 1.2.3