Add instruction of A simple tool to jar up files under directories into JAR files with directory names.

Usage: jars [OPTIONS] DIR1 [DIR2] ...

Available options:
    -f  --force        Remove existing JAR files before generating new one
    -v  --verbose      Print generated JAR file paths
    -vv --veryverbose  Print even more information
    -h  --help         Print this help and exit

Sample:

    $ ls
    test
    $ ls /usr/local/lib
    common
    $ jars test /usr/local/lib/common
    /Users/USERNAME/Documents/test.jar
    /usr/local/lib/common.jar
    $ ls
    test test.jar
    $ ls /usr/local/lib
    common common.jar in README.
Add 'vm.sh' script to simplifiy VBoxManage cli.