Update jekyll plugin to match docs/README.md
Use "hadoop.version" property when specifying Hadoop YARN version too
Allow build configuration to be set in conf/spark-env.sh
Update build docs
Example should make sense
Remove references to unsupported Hadoop versions
Revert "Allow build configuration to be set in conf/spark-env.sh"

This reverts commit 66e7a38a3229eeb6d980193048ebebcda1522acb.
Use Hadoop 1.2.1 in application example
Increase ReservedCodeCacheSize to 256m
Merge pull request #855 from jey/update-build-docs

Update build docs