[Documentation] Adding external blog to documentation

[Rahul Kavale <ka...@gmail.com>]

Hi all,
I recently wrote a blog comparing MapReduce model with that of Apache Spark
trying to explain some important question I think a beginner might have
while exploring Spark.
The blog can be found here:
http://rahulkavale.github.io/blog/2014/11/16/scrap-your-map-reduce/

The blog received quite good audience and I think it might help people who
are just starting to explore Spark and might help them to get their
question cleared regarding comparison of MapReduce model with that of Spark.

I would like to reach it to a broader audience by including it in official
documentation at "External blogs" section at
https://spark.apache.org/documentation.html. I would really like to get
your thoughts on the same.

Thanks & Regards,
Rahul Kavale