tk apply diff is not colored anymore

[pracucci]

I've just upgraded to tanka master and noticed that the diff displayed by tk apply is not colored anymore. The previous version I was running was 0.5 and the output was colored there.

[pstibrany]

I'd prefer an option (ideally one that can be set via env. variable, so that I can turn it off globally) for this. Tanka's built-in coloring always messed up my terminal.

[pracucci]

Tanka's built-in coloring always messed up my terminal.

In my experience tk diff is messing up with colors due to the paging, but not tk apply.

[rfratto]

In my experience tk diff is messing up with colors due to the paging, but not tk apply.

FYI, #210 should fix the problems with colors in tk diff.