Add 'Boolean' as option type to documentation of default (#674)

README.md

@@ -108,7 +108,7 @@ A question object is a `hash` containing question related values:
 `list`, `rawlist`, `expand`, `checkbox`, `password`, `editor`
 - **name**: (String) The name to use when storing the answer in the answers hash. If the name contains periods, it will define a path in the answers hash.
 - **message**: (String|Function) The question to print. If defined as a function, the first parameter will be the current inquirer session answers.
-- **default**: (String|Number|Array|Function) Default value(s) to use if nothing is entered, or a function that returns the default value(s). If defined as a function, the first parameter will be the current inquirer session answers.
+- **default**: (String|Number|Boolean|Array|Function) Default value(s) to use if nothing is entered, or a function that returns the default value(s). If defined as a function, the first parameter will be the current inquirer session answers.
 - **choices**: (Array|Function) Choices array or a function returning a choices array. If defined as a function, the first parameter will be the current inquirer session answers.
 Array values can be simple `strings`, or `objects` containing a `name` (to display in list), a `value` (to save in the answers hash) and a `short` (to display after selection) properties. The choices array can also contain [a `Separator`](#separator).
 - **validate**: (Function) Receive the user input and answers hash. Should return `true` if the value is valid, and an error message (`String`) otherwise. If `false` is returned, a default error message is provided.