Update SimpleWebTokenHandler.cs

I have changed the CreateUnsignedToken method to make use of the CreateClaims method (to reduce duplication) and changes the CreateClaims method to make use of a list based dictionary to enable multiple claims per token.

Need to speak about encoding.... as I have just seen the comment
Update to SWT Handler with tests

Supports multiple claim types.
Merge pull request #16 from GaryMcAllister/patch-1

Update SimpleWebTokenHandler.cs