Suggested changes to 'the tidy data set' section

I've suggested a change from 'row names' to 'column names' as I think this was your intention. 

I re-read Wickham's paper and see instead of 'kind of variable' he used 'observational type'.  I feel this may still be too ambiguous.

I think you may like this cartoon.  I sometimes use ROPRTGRESTA instead of FOO or BAR if I am feeling cheeky.

![dilbertdata2](https://f.cloud.github.com/assets/1305767/1630626/942ba974-574f-11e3-990a-209c0a77adea.png)