Add a man page

Minor fixes and features

Changes since last release:
* Support bright background colors
* Add --no-statusbar to hide the status bar
* Fix search prompt with status bar hidden
* Enabling toggling status bar on / off
* Link to source code from --help output
* Keybinding: 'G' to scroll to the end

Fix startup navigation issues

Before this release, if the input stream was slow at loading, pressing
down arrow would immediately take you to the end of the input.

Also, searching wouldn't find anything.

With this release both arrow-down and searching works even when the
input stream is slow.

Navigation improvements

This release changes 'g' to go-to-line.

Also, it adds ^u and ^d for moving half pages up / down.

Fix suggested $PAGER value in --help output

Before this release, the PAGER= value suggested was hit-or-miss.

With this release, it should be something that you can just use.

Fix coloring on macOS Terminal app

Improve scrolling through wrapped lines

Before this release, if the first line of the screen was wrapped into
two screen lines and you pressed down arrow once, moar scrolled down two
lines, to the next input file line.

With this release, moar now scrolls down one screen line, even in this
case.

Add option for how to render unprintable characters

Try "moar --render-unprintable=whitespace broken-utf8.txt" to prevent
moar from highlighting unprintable characters.

Fixes walles#83

Add --statusbar= command line option

Supports plain, inverse or bold, defaulting to inverse.

Resolves <walles#81>.

Optionally retain screen contents after exit