fix typo

Signed-off-by: Greg Dietsche <Gregory.Dietsche@cuw.edu>

router.go

diff --git a/router.go b/router.go
index 87e1010..3f3d163 100644
--- a/router.go
+++ b/router.go
@@ -93,7 +93,7 @@
 
 // Params is a Param-slice, as returned by the router.
 // The slice is ordered, the first URL parameter is also the first slice value.
-// It is therefore save to read values by the index.
+// It is therefore safe to read values by the index.
 type Params []Param
 
 // ByName returns the value of the first Param which key matches the given name.