[Rd] Suggestion to add crantastic to resources section on posting guide

[Matthew Dowle]

Under the "further resources" section I'd like to suggest the following 
addition :

*  http://crantastic.org/ lists popular packages according to other users 
votes. Consider briefly reviewing the top 30 packages before posting to 
r-help since someone may have already released a package that solves your 
problem.

Thats just a straw man idea so I hope there will be answer, or discussion, 
either way.

Matthew