Add link to Winston Chang's slides

See [his tweet](https://twitter.com/winston_chang/status/484039769265938432)
Small change to text for the Winston Chang link
Add link to Ramnath's slides on rCharts
Merge branch 'patch-1' of github.com:kbroman/user2014.github.io into kbroman-patch-1

Conflicts:
	index.html

Closes #2
Add link to Winston Chang's slides

See [his tweet](https://twitter.com/winston_chang/status/484039769265938432)
Small change to text for the Winston Chang link
Add link to Ramnath's slides on rCharts
Uploaded data.table talk
Added link to slides
added slides (in brackets)
Slides for testR talk
tutorial and talk materials of Yihui Xie
Merge branch 'kbroman-patch-1'