Use cgo-free SQL driver and add limit of 100 to maxVoters

cmd/web/handlers.go

@@ -72,6 +72,7 @@ func (r *createElectionRequestWithValidator) isValid() bool {
 	r.CheckField(validator.After(r.ExpiresAt, time.Now()), "expiresAt", "must expire in a future date")
 	r.CheckField(validator.GreaterThan(len(r.Choices), 1), "choices", "there must be more than 1 choice")
 	r.CheckField(validator.UniqueValues(r.Choices), "choices", "must not contain duplicate values")
+	r.CheckField(validator.LesserThan(r.MaxVoters, 101), "maxVoters", "cannot create a known-voters election with more than 100 voters")
 
 	for _, choice := range r.Choices {
 		r.CheckField(validator.NotBlank(choice), "choice", "must not be blank")