*: add/fix godoc comments to satisfy golint

Fixes things like:
 * exported type/method/function X should have comment or be unexported
 * comment on exported type/method/function X should be of the form "X ..."
   (with optional leading article)

Refs. #213.

examples/storage/storage.go

@@ -4,6 +4,7 @@ import (
 	"github.com/CityOfZion/neo-go/pkg/interop/storage"
 )
 
+// Main is a very useful function.
 func Main(operation string, args []interface{}) interface{} {
 	ctx := storage.GetContext()