LaTeX writer: Fix tables

- [x] Fix a bug introduced in 66378062b622b0815a1a2ddce5d557e3ad13330c, which
  causes the table caption to repeat across all pages
- [x] Address the issues discussed
  [here](https://groups.google.com/forum/#!msg/pandoc-discuss/qMu6_5lYy0o/ZAU7lzAIKw0J)
  regarding the extra vertical space.
  - [ ] NOTE: This will cause multiline table cells to appear unpadded. See
    http://tex.stackexchange.com/questions/34971
  - [x] Use [`\tabularnewline`](http://tex.stackexchange.com/questions/78796)
    instead of `\\`.
LaTeX writer: Add `\strut` to fix multiline tables

See: http://tex.stackexchange.com/questions/34971
Merge branch 'ugly-tables' of https://github.com/jlduran/pandoc into jlduran-ugly-tables