Allow users to include Phpakefile

[jigarius]

Requirements

If a user wants to organize their commands into different Phpakefile, they can include one Phpakefile from another like:

require('path/to/Phpakefile1')
require('path/to/Phpakefile2')
require('path/to/Phpakefile3')

This should work by default, but need to test it so that it can be called done.