Make it clearer that Stratosphere is not build upon Hadoop

[twalthr]

The website does not emphasize enough that Stratosphere has its own MapReduce runtime and does not use Hadoop's MapReduce.

At the beginning I also through that Stratosphere uses Hadoop.

Some statements like

"It combines the strengths of MapReduce/Hadoop with powerful programming abstractions in Java" on the first page.

and

"Stratosphere for Hadoop 1/Hadoop 2" in the download section are very misleading.

In my opinion in the download section we should completely leave out the term "Hadoop" and use "HDFS" instead.

Maybe we can prevent questions like the most recent one:
https://groups.google.com/forum/#!topic/stratosphere-dev/-WSxxtsdCSo

[fhueske]

Hmm, good point!

[fhueske]

See also this issue

[rmetzger]

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