Yahoo.com

- [x] 150px image
- [x] Add Waltz log in/out on main site and all subdomains.
- [ ] Facilitate password re-input screen (i.e., https://login.yahoo.com/config/login_verify2) that Yahoo displays before allowing user to edit account settings.
 * Is this possible in Waltz's current form? Do we need a new parameter for this scenario? I think Amazon does a similar thing: require password re-entry for certain actions even though user is already logged in.
- [ ] Facilitate Yahoo's [second sign in verification](http://help.yahoo.com/kb/index?locale=en_US&page=content&id=SLN5013). Presently, enabling second sign in changes the default login page and breaks Waltz functionality. The current `twoFactor` parameter does not appear ready to handle Yahoo's idiosyncratic multi-factor process.
- [x] Hand this hot potato off to the professionals @jessepollak and @josephwegner :-)