Passthrough Babushka::ANSI.wrap when we're not on a terminal.

Colour is already correctly enabled and disabled when babushka is run
from the command line and the cmdline parser is in use. This patch
also disables colour for non-terminal output when logging directly
from the specs or similar.
No need to set a default colour on/off option anymore.

Now that Babushka::ANSI handles turning colour on and off, we don't need to set an option for it when parsing the commandline.
Check stdout instead of stdin for ANSI: that's what we're writing to.
Default to installing 'nodejs', which is what most pkg managers use.

I made this change to fix the dep for arch, which uses 'nodejs'. But most other systems (yum & gentoo among others) use 'nodejs' too. One exception is freebsd, which uses 'node' like brew; I've added a case for it here.
Merge branch 'ansi'