Fix Broken Mousewheel in Firefox

Unit Tests
-------------

- Added tests for mousewheel detection branches.

How To +10/QA
-------------

```bash
# skip the following steps if you've already initialized the project
$ git clone git@github.com:WebFilings/wf-common.git
$ cd wf-common

# do not skip these!
$ git fetch && 
git checkout HY-556_fix_broken_mousewheel_firefox && 
./init.sh && 
grunt qa
```

- Should see no console errors.
- `bower link wf-common` in the master branch of wf-uicomponents.
- `grunt serve` in wf-uicomponents.
- Navigate to ScrollList example in firefox.
- Using mousewheel, try scrolling. _Should scroll as you'd expect_.
- `git checkout master` in wf-common to compare with existing behavior.
- Refresh the ScrollList example in firefox.
- Try scrolling. _Should have some troubles_.

@lancefisher-wf 
@robbecker-wf 
@patkujawa-wf