better docker instructions

Author: tansengming

README.md

@@ -51,7 +51,7 @@ You can chat with ELIZA on the CLI by running:
 
 If you already have Docker installed, here's how you can get started:
 
-- `docker build -t eliza-rb https://github.com/tansengming/eliza-rb.git#master`
+- `docker build -t eliza-rb github.com/tansengming/eliza-rb`
 - `docker run -it eliza-rb`
 
 # Development