Fix warning and generated path when file above basedir

Trying to generate autoloader for phpdocumentor/reflection-docblock

     $ phpab \
           --basedir src/phpDocumentor/Reflection/DocBlock \
           --output src/phpDocumentor/Reflection/DocBlock/autoload.php \
           src/phpDocumentor/Reflection
     phpab 1.16.2 - Copyright (C) 2009 - 2014 by Arne Blankerts
     Scanning directory src/phpDocumentor/Reflection
     Notice: Undefined offset: 11 in /usr/share/php/TheSeer/Autoload/AutoloadRenderer.php on line 220
     Autoload file src/phpDocumentor/Reflection/DocBlock/autoload.php generated.

And in generated autoloader (double /)

                'phpdocumentor\\reflection\\docblock' => '/..//DocBlock.php',

This should fix both