Add: global command

[BrianHenryIE]

I don't really like the manner that global classes' class names are prefixed, I'd prefer global classes were moved into a namespace.

strauss global --namespace Company\\Project --paths src/,my-plugin.php

<?php

class LivingDangerously {
}

before

<?php

class Safely_LivingDangerously {
}

instead

<?php

namespace Safely;

class LivingDangerously {
}

Edit: it makes sense to tackle #74 at the same time. I.e. make Strauss aware of functions.