Minor clarification in the README

Author: rgorsuch

README.md

@@ -81,8 +81,8 @@ n := s.Names()            // Get a []string
 f := s.Field(name)        // Get a *Field based on the given field name
 f, ok := s.FieldOk(name)  // Get a *Field based on the given field name
 n := s.Name()             // Get the struct name
-h := s.HasZero()          // Check if any field is initialized
-z := s.IsZero()           // Check if all fields are initialized
+h := s.HasZero()          // Check if any field is uninitialized
+z := s.IsZero()           // Check if all fields are uninitialized
 ```
 
 ### Field methods