ShiftOut proposal implementation

As mention by Diego DE UNA GOMEZ in its email on list[1], we've done the beginning of an implementation of the first ShiftOut proposal[2] in Standart Firmata. It is probably wrongly done but could we have help from you to improve it in order to integrate it ?

[1] : http://sourceforge.net/mailarchive/forum.php?thread_name=20120717154657.19826hrmecn1t8eo%40webmail.enseirb-matmeca.fr&forum_name=firmata-devel
[2] : http://firmata.org/wiki/Proposals#ShiftOut_Proposal