Trigger other commands from the default one

[mitogh]

Steps to reproduce and a minimal demo of the problem

Once we just type the name of the generator we should ask if the user wants to trigger a specific generator.

Current behavior

Available commands are printed

Expected/desired behavior

• Ask for the command to be executed (using numbers, maybe?)

yo moxie-lean              

     _-----_
    |       |    .--------------------------.
    |--(o)--|    |    Welcome to the Lean   |
   `---------´   |  generator. This is the  |
    ( _´U`_ )    |  list of some available  |
    /___A___\    |        generators.       |
     |  ~  |     '--------------------------'
   __'.___.'__   
 ´   `  |° ´ Y ` 

Try to run: yo moxie-lean:<subcommand> to use any of this generators. List of subcommands
1. php-lib
2. new-wp
3. new-wp-project
4. new-wp-plugin

Command to execute: [1-4]

Other information