Fix a hang on Unix

Fancy shutdown, fancy problems, let's hope this release has no races.

Tail files, not just streams

With this release, if you open a (log?) file in moar, and more lines are
added to the file after you start moar, moar will pick up the new lines
and display them.

Also, if you have a terminal editor (nano, vim etc), and press "v" to
edit a file, moar will now not steal the first byte from your editor any
more. Improved on Unix, Windows unchanged, PRs welcome.

Fix shutdown problems on Windows

Actually tested on Windows.

Fix editing files on Windows

Before this release, pressing 'v' to edit a file on Windows would tell
you your editor was not executable.

With this release, executability detection on Windows should now work.

Support opening piped input in editor

By pressing 'v'.

Before this change, 'v' only worked for actual files.

With this change in place, 'v' will also work for piped input.

Piped input will be written into a temporary file, and then the editor
will be opened with that file.

Fix a shutdown issue

Take II.

Fix crash with --quit-if-one-screen

Fix terminal editor lagginess

Before this release, if you pressed 'v' to open the current file in your
$EDITOR, and the editor was terminal based (think vim, nano), then the
editor was really laggy.

That lagginess has been fixed in this release.

Support pressing 'v' to launch an editor

With this release, if you press 'v' while viewing a file, moar will
launch an editor to edit the file. The editor is determined by the
$VISUAL and $EDITOR environment variables.

Fixes #211.

Faster search in large files

Before this release, searching was single threaded.

With this release, searching now uses all available cores, which makes
searching large files a lot faster.