Removed sbt folder and changed docs accordingly

README.md

docs/README.md

docs/_plugins/copy_api_dirs.rb

docs/api.md

docs/hadoop-third-party-distributions.md

docs/index.md

docs/python-programming-guide.md

docs/quick-start.md

docs/running-on-yarn.md

docs/scala-programming-guide.md

make-distribution.sh

pyspark

run-example

sbt/sbt

sbt/sbt-launch-0.11.3-2.jar

sbt/sbt.cmd

spark-class