I know I'ved used the naming convention of `Check*()` for similar functions elsewhere that return `bool`s.  And apparently `gists.go` includes a `Starred()` method with no prefix.  I don't have strong feelings about what prefix is used, but it should probably be consistent, unless there's particular reason not to.

(`time.Time` does have the `IsZero()` func, which leans toward your naming convention here.  Do you know if the stdlib has conflicting examples?)