Consider support for tab-based indent, if only programmatically

[JakeWharton]

I would like to produce formatting with tabs, and this is currently impossible to do due to internal modeling.

Tabs generally have a column-based width associated with them. I use two columns to achieve the same look as two space indent, for example. This allows the algorithms based on line length to still work correctly.

In output, however, spaces are hard coded to be used to represent indent values.