Build a custom TimeAxis

Decide if we need to do this. But some thoughts are:
1) Make it so that context is always present (i.e. even zoomed into a day, make sure its clear what year and month you are looking at)
2) Possibly support scales that don't include weekends
3) Should support forced hour, day, month and year views. e.g. if you want to show a month and have each day on the axis (i.e. not let d3 skip any), that should be possible.
4) Should support relative scale (i.e. a time scale starting at 0 and showing relative time)