Version number bump.

Nothing functional changing here; just forgot to sign the files when I published the 3.0 release to PowerShellGet, and I can't fix that without pushing a new version number.
Made signing default behavior of psake build script.

So I don't forget in the future.  This means other people using my psake build script will need to specify that they're only using Build and not Sign (since Sign depends on my code-signing cert), but oh well.
Merge pull request #10 from dlwyatt/v3.0.1

V3.0.1