* Refactor deprecated `getOrCreate()` in spark 3
* Compile with scala 2.12
* Updated usage related to obsolete/deprecated features
* remove use of scala-logging replaced by using slf4j directly
After this you should be able to use the library in the shell as follows:
```
bin/spark-shell --packages com.databricks:spark-sql-perf:0.2.3
```
Author: Michael Armbrust <michael@databricks.com>
Closes#46 from marmbrus/publishToMaven.