Support omitting first and last corner

[fancsali]

Many MarkDown flavours - and lazy people alike - prefer not to have the | characters added at the sides of tables.

In other words, instead of this:

| foo | bar | baz |
| 1     |    2  |     3 |

one would use:

foo | bar | baz
1     |    2  |     3

However, at the moment if using the latter format table-mode would not recognise the table - at least not for the \tr mapping and :TableModeRealing in general.

Can this feature be added perhaps?