Update documentation for in() Fix conditional. (#235)

Author: blackwinter

README.md

@@ -644,7 +644,8 @@ Executes the functions if/unless the field value matches the regular expression
 Executes the functions if/unless the field value does not match the regular expression pattern. If it is an array or a hash none of the field values may match the regular expression pattern.
 
 #### `in`
-Executes the functions if/unless the field value is identical to a value in a given field.
+
+Executes the functions if/unless the field value is contained in the value of the other field.
 
 ## Xtext