Update to Line/Bar.prototype.onHoverOut

I have never edited/contributed to a Repo before so I hope I don't cause World War 3 somehow.

I just found Morris.js yesterday, and while I was testing it out I noticed that my chart legend remained displayed after my mouse left the chart area.

After looking at the source code, I believe both Line/Bar.prototype.onHoverOut should be changed to !== false.  I tested this problem/change on Mac OS using latest versions of Chrome, Firefox, Safari and Opera.  Problem ceased to exist in all browsers after my change from === 'auto' to !== false