This PR adds a --autoload (shorthand -a) option to boris. Adding this option will make Boris automatically search for a autoload.php file and require it so that the user's classes are available immediately.

Examples:

Using -a option, autoload.php is required automatically:

~/my_composer_project$ boris -a
Requiring autoload file: /Users/leonardoraele/my_composer_project/vendor/autoload.php
[1] boris> 

Not using -a option, boris works normally.

~/my_composer_project$ boris
[1] boris> 

Using -a option not in a composer project, nothing is loaded. Boris works normally.

~/my_composer_project$ cd ~
~$ boris -a
No autoload file found.
[1] boris>