[SPARK-1964][SQL] Add timestamp to HiveMetastoreTypes.toMetastoreType

Author: Michael Armbrust <michael@databricks.com>

Closes #1061 from marmbrus/timestamp and squashes the following commits:

79c3903 [Michael Armbrust] Add timestamp to HiveMetastoreTypes.toMetastoreType()

sql/hive/src/main/scala/org/apache/spark/sql/hive/HiveMetastoreCatalog.scala

@@ -237,6 +237,7 @@ object HiveMetastoreTypes extends RegexParsers {
     case BinaryType => "binary"
     case BooleanType => "boolean"
     case DecimalType => "decimal"
+    case TimestampType => "timestamp"
   }
 }