update fragmentSelector to return Integer values instead of String

__tests__/src/lib/AnnotationResource.test.js

@@ -53,11 +53,11 @@ describe('AnnotationResource', () => {
   describe('fragmentSelector', () => {
     it('simple string', () => {
       expect(new AnnotationResource({ on: 'www.example.com/#xywh=10,10,100,200' })
-        .fragmentSelector).toEqual(['10', '10', '100', '200']);
+        .fragmentSelector).toEqual([10, 10, 100, 200]);
     });
     it('more complex selector', () => {
       expect(new AnnotationResource({ on: { selector: { value: 'www.example.com/#xywh=10,10,100,200' } } })
-        .fragmentSelector).toEqual(['10', '10', '100', '200']);
+        .fragmentSelector).toEqual([10, 10, 100, 200]);
     });
   });
 });

src/lib/AnnotationResource.js

@@ -37,9 +37,9 @@ export default class AnnotationResource {
     const { on } = this.resource;
     switch (typeof on) {
       case 'string':
-        return on.match(/xywh=(.*)$/)[1].split(',');
+        return on.match(/xywh=(.*)$/)[1].split(',').map(str => parseInt(str, 10));
       case 'object':
-        return on.selector.value.match(/xywh=(.*)$/)[1].split(',');
+        return on.selector.value.match(/xywh=(.*)$/)[1].split(',').map(str => parseInt(str, 10));
       default:
         return null;
     }