Remove Dryad

Too much overlap with MapReduce + Spark.

Author: rxin

README.md

@@ -75,8 +75,6 @@ Columnar storage and column-oriented query engine are critical to analytical wor
 
 * [Spanner](http://static.googleusercontent.com/media/research.google.com/en//archive/spanner-osdi2012.pdf) (2012): Spanner is "a scalable, multi-version, globally distributed, and synchronously replicated database". The linchpin that allows all this functionality is the TrueTime API which lets Spanner order events between nodes without having them communicate. [There is some speculation that the TrueTime API is very similar to a vector clock but each node has to store less data](http://www.cse.buffalo.edu/~demirbas/publications/augmentedTime.pdf). Sadly, a paper on TrueTime is promised, but hasn't yet been released.
 
-* [Dryad: Distributed Data-Parallel Programs from Sequential Building Blocks](http://cs.brown.edu/~debrabant/cis570-website/papers/dryad.pdf) (2007): Dryad is a programming model developed at Microsoft that enables large scale dataflow programming. "The fundamental difference between the \[MapReduce and Dryad\] is that a Dryad application may specify an arbitrary communication DAG rather than requiring a sequence of map/distribute/sort/reduce operations". 
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 ## <a name='consensus'> Consensus and Consistency