Update README.md

Author: codingchili

README.md

@@ -28,7 +28,7 @@ To compile the binary module argon2-ffi build tools are requried, install with
 windows: 
   npm install --global --production windows-build-tools
 unix:    
-  sudo apt-get install -y build-essential
+  sudo apt-get install build-essential libssl-dev libffi-dev python-dev
 ```
 This installs MS build tools and python 2.7 and is required for node-gyp to work.