fix typo

Author: SimonWaldherr

Diff for: between/between_test.go

@@ -1,6 +1,6 @@
 // Package between compares the performance of checking
-// if a number is between to other numbers via regex
-// and by parsing the number as integer.
+// if a number is between two other numbers via regex
+// and by parsing the number as integers.
 package between
 
 import (

Diff for: concat/concat_test.go

@@ -1,6 +1,6 @@
 // Package concat benchmarks the performance of
-// various string concatination methods.
-// Instead of just concat a string to another string
+// various string concatenation methods.
+// Instead of just concatenating a string to another string
 // it is also possible (and much faster) to use
 // a bytes buffer.
 package concat