Add section(s) on HTML parsing? on ghost browsers? (with examples for R)

[briatte]

e.g. for R, HTML parsers:

• XML - XML and HTML scraper and parser. Also works via FTP.
• xml2 - R wrapper for the libxml2 C library.

e.g. for R, ghost browsers:

• RSelenium - R bindings for the Selenium 2.0 WebDriver.
• I think RStudio is working on something similar, but cannot find it any more