Slider: moved events to named functions

[dominicbarnes]

Originally, I created an issue for the Widget Factory not allowing events with namespaces, but the better solution was to move the event handlers for the slider into named functions so plugins/extensions to base widgets can hook in and not conflict with bound event handlers.

[scottgonzalez]

Landed in 176e0ed.

I updated your email address in the git commit info to match the address you used when you signed the CLA. In the future, it would help if you could either use the other address or sign the CLA again with the email address you intend to use for contributions.

Thanks.

[dominicbarnes]

@scottgonzalez I went ahead and signed the CLA again using my work email (dbarnes@treetopllc.com, since that is the one my github account is tied to, and the one all my commits are logged under)

[scottgonzalez]

Thanks.