* New modes that either print it only when it isn't the first line, or
only add it (as well as a warning) if the last command didn't return
a newline.
* Overengineered af.
* Ascii and Blocks themes need to use the terminal's defaults,
otherwise they will leave a black smear on a non-black terminal
background.
* Replace -1 colors with SECTION_DEFAULT
The script no longer contains theme definitions, and the default
configuration has been made much simpler. Existing themes have been
moved to a bunch of files (one file per theme) in a subdirectory.