Added SetCategories() method to support multiple categories.  SetCategory() left to maintain backward compatibility.
NUnit test added for SetCategories()
Merge pull request #31 from bobmclaren/master

Added support for multiple categories.
Merge branch 'master' of github.com:sendgrid/sendgrid-csharp into bw-net45
cleanup example
remove restsharp link
clean up dependencies
working on uploads
cleanup example, fix attachments
bump version
add nuspec and nupkg