Update userSettings.conf

"java" should not be hardcoded into BIG_BENCH_DATAGEN_HADOOP_JVM_ENV but should be a configurable parameter. In some cases absolute path for java would need to be specified (as BIG_BENCH_DATAGEN_EXEC). This would resolve issue #6.
Merge pull request #7 from nishkamravi2/patch-1

Update userSettings.conf