Page auto scrolls up when element is selected

[kathyoleary]

In order to use less of my time As a LMHT user I want the page to automatically scroll up to where I can see all the content, when I select an element from the dropdown within the sticky nav.

Acceptance Criteria:

• When the new content loads, the page scrolls up to the beginning of the new content
• The transition is smooth

Given a LMHT user, When I am scrolled down, And sticky nav appears with the combobox in it, And I select an element, Then the page automatically scrolls up to where I can see all the new content displayed.

[ericanaughton]

merged to adorable master