A number of minor issues crept in as the output plugins were refactored.

Ensure `padding_len` is greater than 0.  When calculating the terminal
width, if the output is piped, we can end up with a negative padding
length.  This results in no space between the filename the size.  Set
`padding_len` to a minimum of 1.

The `-` lines printed by `_getHardRule()` are too short when output is
not to a terminal, i.e.: when sending to a pager.  This turns out to be
due to the LINES and COLUMNS being transposed in `getTtySize`.  When the
terminal size cannot be determined, we want to set it to something like
80x24 (COLUMNS x LINES), but instead we set it to 25x78, which results
in very short lines from `_getHardRule()`.  Fix the transposition and
adjust the values to 79x25 which ensures the output is aligned with
`printAudioInfo()`.  The audio info line uses two hard tabs and has a
minimum width of 79 COLUMNS.

Fix an off-by-one in the `size_len` var in `_getFileHeader()`.  We add 4
characters (`[ ` & ` ]`) rather than 5.  This was added in 599eddd
(display the ellipsis file name and path, and the file size right
justified in printHeader., 2015-10-20), released in 0.7.9.

The output is now neatly aligned when output is not directly to a
terminal:

$ eyeD3 ~/mp3/tool/ænima/13-ænema.mp3 | cat
/home/foo/mp3/tool/ænima/13-ænema.mp3                              [ 14.50 MB ]
-------------------------------------------------------------------------------
Time: 06:40	MPEG1, Layer III	[ ~278 kb/s @ 44100 Hz - Joint stereo ]
-------------------------------------------------------------------------------