Keyboard shortcut for changing date preset: d (day), w (week), m (month), y (year)

[dannyvankooten]

Quoting @rghedin in #237:

I noticed that Koko Analytics demands three mouse clicks to change pre-sets of date range. Maybe too many? 😄

Since left and right arrows are already present in Koko, I was wondering if it would be possible to add other shortcuts for pre-sets, at least to cycle date views (day only, weekly, monthly, and year). Maybe d, w, m, and y?