fix: typo in README.md regarding docker image base in Dockerfile

Author: IYaksha

README.md

@@ -788,7 +788,7 @@ export NVM_DIR="$HOME/.nvm"
 
 ## Docker For Development Environment
 
-To make the development and testing work easier, we have a Dockerfile for development usage, which is based on Ubuntu 14.04 base image, prepared with essential and useful tools for `nvm` development, to build the docker image of the environment, run the docker command at the root of `nvm` repository:
+To make the development and testing work easier, we have a Dockerfile for development usage, which is based on Ubuntu 16.04 base image, prepared with essential and useful tools for `nvm` development, to build the docker image of the environment, run the docker command at the root of `nvm` repository:
 
 ```sh
 $ docker build -t nvm-dev .