[SPARK-6863] Fix formatting on SQL programming guide.

https://issues.apache.org/jira/browse/SPARK-6863

Author: Santiago M. Mola <santiago.mola@sap.com>

Closes #5472 from smola/fix/sql-docs and squashes the following commits:

42503d4 [Santiago M. Mola] [SPARK-6863] Fix formatting on SQL programming guide.

(cherry picked from commit 6437e7c)
Signed-off-by: Michael Armbrust <michael@databricks.com>

docs/sql-programming-guide.md

@@ -1784,6 +1784,7 @@ in Hive deployments.
 
 
 **Esoteric Hive Features**
+
 * `UNION` type
 * Unique join
 * Column statistics collecting: Spark SQL does not piggyback scans to collect column statistics at