Merge branch '3.4' into 4.3

* 3.4:
  Make clear when the options are effectively required

Author: javiereguiluz

reference/constraints/Count.rst

@@ -125,8 +125,10 @@ max
 
 **type**: ``integer``
 
-This required option is the "max" count value. Validation will fail if the
-given collection elements count is **greater** than this max value.
+This option is the "max" count value. Validation will fail if the given
+collection elements count is **greater** than this max value.
+
+This option is required when the ``min`` option is not defined.
 
 maxMessage
 ~~~~~~~~~~
@@ -150,8 +152,10 @@ min
 
 **type**: ``integer``
 
-This required option is the "min" count value. Validation will fail if the
-given collection elements count is **less** than this min value.
+This option is the "min" count value. Validation will fail if the given
+collection elements count is **less** than this min value.
+
+This option is required when the ``max`` option is not defined.
 
 minMessage
 ~~~~~~~~~~