Add jest and simple test

tests/components/TagListItem.snapshot.test.js

@@ -0,0 +1,9 @@
+import React from 'react'
+import renderer from 'react-test-renderer'
+import TagListItem from 'browser/components/TagListItem'
+
+it('TagListItem renders correctly', () => {
+  const tagListItem = renderer.create(<TagListItem name='Test' handleClickTagListItem={jest.fn()} />)
+
+  expect(tagListItem.toJSON()).toMatchSnapshot()
+})

tests/components/__snapshots__/TagListItem.snapshot.test.js.snap

@@ -0,0 +1,19 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`TagListItem renders correctly 1`] = `
+<button
+  className="tagList-item"
+  onClick={[Function]}
+>
+  <span
+    className="tagList-item-name"
+  >
+    # Test
+    <span
+      className="tagList-item-count"
+    >
+       
+    </span>
+  </span>
+</button>
+`;