add native support for Emacs Org-mode tables

[maxecharel]

Hi, while you indicated that Pandoc was supporting Org-mode tables (#1372), I thought it would be nice to have native support in knitr. I therefore gave it a go :) No major changes/adjustment, I didn't want to mess with the well oiled mechanic of table.R ;)

kable(x = head(iris), format = "org", caption = "test")

#+CAPTION: test
| Sepal.Length| Sepal.Width| Petal.Length| Petal.Width|Species |
|-------------+------------+-------------+------------+--------|
|          5.1|         3.5|          1.4|         0.2|setosa  |
|          4.9|         3.0|          1.4|         0.2|setosa  |
|          4.7|         3.2|          1.3|         0.2|setosa  |
|          4.6|         3.1|          1.5|         0.2|setosa  |
|          5.0|         3.6|          1.4|         0.2|setosa  |
|          5.4|         3.9|          1.7|         0.4|setosa  |

[yihui]

Also needs a bullet in NEWS.md. Thank you!

[CLAassistant]

All committers have signed the CLA.

[yihui]

@maxecharel Would you please sign the CLA? I have basically rewritten your implementation, but it will still be great if you can sign the contributor agreement so that you don't need to sign it again if you want to make further contributions in future. Thanks!

[maxecharel]

Hi @yihui , apologies for the delay in my response; I just see that you've accomplished quite a bit! Unfortunately I had to let my already very limited 'github activity' aside due to time allocation issues, but thank you for all your work :) I have signed the CLA ;)

[yihui]

No worries! Thank you anyway! I just happen to be allocating time mainly to Github projects recently :)