Rename package to pack
Prepare for next version
Import more example source codes
Add Javadoc
Create package vm and move classes into it
Build a new command model
Extract DefaultCommandFactory from CommandFactory
Add methods to CommandListExecutor
Edit classes to fit new command model
Divide WhitespaceParser from Interpreter
Import more example source codes
Add PseudoCodeGenerator and edit CLI program
Clean up pack directory
Merge branch 'master' into release

Ready for release