Comment on constant - travis deps

.travis.yml

@@ -3,5 +3,8 @@ language: go
 go:
   - 1.4
 
+install:
+  - go get "code.google.com/p/rsc/qr"
+
 script:
   - go test -v ./...

totp.go

@@ -23,7 +23,7 @@ import (
 const (
 	BACKOFF_MINUTES = 5 // this is the time to wait before verifying another token
 	MAX_FAILURES    = 3 // total amount of failures, after that the user needs to wait for the backoff time
-	COUNTER_SIZE    = 8
+	COUNTER_SIZE    = 8 // this is defined in the RFC 4226
 )
 
 type totp struct {