Added support for Raspberry Pi model B.

[groupmsl]

I've got quite an early Raspberry Pi model B, and when I tried to use the raspberry-sharp-io library I got errors because it didn't know about my processor type. I've simply added this, and tested with my Pi.

My Pi: $cat /proc/cpuinfo processor : 0 model name : ARMv6-compatible processor rev 7 (v6l) BogoMIPS : 697.95 Features : half thumb fastmult vfp edsp java tls CPU implementer : 0x41 CPU architecture: 7 CPU variant : 0x0 CPU part : 0xb76 CPU revision : 7

Hardware : BCM2835 Revision : 000f Serial : XXX