docs: fix readme examples (#14)

README.md

@@ -3,16 +3,17 @@ unique-filename
 
 Generate a unique filename for use in temporary directories or caches.
 
-```
-var uniqueFilename = require('unique-filename')
+```js
+const uniqueFilename = require('unique-filename')
 
-// returns something like: /tmp/912ec803b2ce49e4a541068d495ab570
-var randomTmpfile = uniqueFilename(os.tmpdir())
+// returns something like: '/tmp/c5b28f47'
+const randomTmpfile = uniqueFilename(os.tmpdir())
 
-// returns something like: /tmp/my-test-912ec803b2ce49e4a541068d495ab570
-var randomPrefixedTmpfile = uniqueFilename(os.tmpdir(), 'my-test')
+// returns something like: '/tmp/my-test-51a7b48d'
+const randomPrefixedTmpfile = uniqueFilename(os.tmpdir(), 'my-test')
 
-var uniqueTmpfile = uniqueFilename('/tmp', 'testing', '/my/thing/to/uniq/on')
+// returns something like: '/my-tmp-dir/testing-7ddd44c0'
+const uniqueTmpfile = uniqueFilename('/my-tmp-dir', 'testing', '/my/thing/to/uniq/on')
 ```
 
 ### uniqueFilename(*dir*, *fileprefix*, *uniqstr*) → String