Allow to display Axis.Time labels like in Axis.Category.

Close #1130.

4 different configurations of "center" and "between" layouts

http://jsfiddle.net/kr5eapzt/41/

![screen shot 2014-12-18 at 3 55 44 pm](https://cloud.githubusercontent.com/assets/8551049/5498101/7cfc916e-86ce-11e4-865d-3768b6992c0c.png)

function name is inapt.  When I read it, it seems to be implying that we hide all the labels when the code seems to suggest that we're only hiding labels that don't fit/overlap