Fixing composer.sh, ref #491

[stefantalen]

Altering the arguments so they are being processed correctly.

My knowledge of bash scripts isn't that great, but using these changes fixed the issue I had (#491)

[fideloper]

howdy!

I'm not sure using sudo would be a real fix here, in theory installing packages globally can/should still be per user (well, that seems to be a matter of opinion).

I think we can make use of the COMPOSER_HOME environment variable, explicitly, in this installer script as an alternative. Example: https://coderwall.com/p/ma_cuq/using-composer-to-manage-global-packages

[stefantalen]

Updated the pull request, I've ran vagrant provision multiple times and still haven't had any errors so I guess it is save to use.

[fideloper]

Cool, let's try that out -thanks for giving it some tests as well :D