Don't require the spark home environment variable to be set for standalone mode (change needed by SIMR)

Extend QuickStart to include next steps

Various UI tweaks

Doc improvements for 0.8

- Use "fluid" layout that can expand to wide browser windows, instead of
  the old one's limit of 1200 px
- Remove unnecessary <hr> elements
- Switch back to Bootstrap's default theme and tweak progress bar colors
- Make headers more consistent between deploy and app UIs
- Replace some inline CSS with stylesheets

spark-daemon

and new Python stuff

Pyspark sampling function

Don't send SIGINT / ctrl-c to Py4J gateway subprocess

PySpark: implementing subtractByKey(), subtract() and keyBy()

Make HadoopRDD's configuration accessible

Fix broken build by removing addIntercept

Adding linear regression and refactoring Ridge regression to use SGD

Change SVM to use {0,1} labels

Change build and run instructions to use assemblies

Fix removed block zero size log reporting

are now needed

This includes the following changes:
- The "assembly" package now builds in Maven by default, and creates an
  assembly containing both hadoop-client and Spark, unlike the old
  BigTop distribution assembly that skipped hadoop-client
- There is now a bigtop-dist package to build the old BigTop assembly
- The repl-bin package is no longer built by default since the scripts
  don't reply on it; instead it can be enabled with -Prepl-bin
- Py4J is now included in the assembly/lib folder as a local Maven repo,
  so that the Maven package can link to it
- run-example now adds the original Spark classpath as well because the
  Maven examples assembly lists spark-core and such as provided
- The various Maven projects add a spark-yarn dependency correctly