fix: change boolean to bool (#113)

luisvt · Kent C. Dodds · commit 04df99d001c9 · 2017-06-27T10:26:27.000-06:00
change `boolean` to `bool` to correct next error:

```
TypeError: Cannot read property 'optional' of undefined
```
diff --git a/src/types/select.js b/src/types/select.js
@@ -28,7 +28,7 @@ export default  ngModule => {
           labelProp: check.string.optional,
           valueProp: check.string.optional,
           groupProp: check.string.optional,
-          notNull: check.boolean.optional,
+          notNull: check.bool.optional,
           nullDisplay: check.string.optional
         }
       })

Original file line number	Diff line number	Diff line change
`@@ -28,7 +28,7 @@ export default ngModule => {`
`28`	`28`	`labelProp: check.string.optional,`
`29`	`29`	`valueProp: check.string.optional,`
`30`	`30`	`groupProp: check.string.optional,`
`31`		`- notNull: check.boolean.optional,`
	`31`	`+ notNull: check.bool.optional,`
`32`	`32`	`nullDisplay: check.string.optional`
`33`	`33`	`}`
`34`	`34`	`})`