Merging Refactor -> master

Added nuspec

Fixes to build.ps1

Added NUnit.Runners.2.6.4

Added Kingsland.PiFaceSharp.NuGet sample program

Merge pull request #4 from mikeclayton/refactor

Added *.nuspec file

Added NUnit.Runners.2.6.4 package

Cleaned up some namespace references

Updated build scripts

Cleaned up some resharper warnings

Cleand up some resharper warnings

Added output pins to SampleClient

added unite tests for PiFaceDevice

Added ISpiDevice interface and VirtualSpiDevice class to allow for unit testing PiFaceDevice