Change Markdown table formatter

[Taichi Ishitani]

Change Markdown table formatter from ruport to table-formatter.

Reason:

• It's seemed that ruport is not active.
• The table-formatter is very simple and it is enough.

[Taichi Ishitani]

The table-formatter does not escape newline code.
To use it, jrobertson/table-formatter#1 should be merged.

[Taichi Ishitani]

The table-formatter does not escape newline code.
To use it, jrobertson/table-formatter#1 should be merged.

This PR has not yet been merged so I abandon use of the table-formatter gem.