Add OnelineFormat

```diff
 Usage: table_beet [options]
         --output        Directory to output (default: ./stepdoc)
         --path          Directory that contains step file. (default: ./spec)
         --suffix        Suffix of step file  (default: _steps.rb)
     -n, --textmode      Display steps in plain text (No generate HTML)
+    -s, --oneline       Display steps in plain text (short mode)
     -v, --version       Print this version
     -h, --help          Display this help message.
```