Some niceties for _.sample.

* Use consistent args check.
* Handle objects in the single value path.
Add favicon to test/index.html
Merge pull request #1283 from braddunbar/icon

Add favicon to test/index.html
No need to be clever.
Use _.values for sampling objects.
Merge pull request #1282 from braddunbar/sample

Some niceties for _.sample.