Change cast to unwrap.

If using some sort of pool libraries (like c3p0 or HikariCP) - got ClassCastException, but unwrap always working good.

Author: Mikhail Akushsky

src/main/java/de/zalando/typemapper/core/TypeMapper.java

@@ -76,7 +76,7 @@ private ResultTree extractResultTree(final ResultSet set) throws SQLException {
         LOG.trace("Extracting result tree");
 
         // cast to obtain more information from the result set.
-        final Jdbc4ResultSet pgSet = (Jdbc4ResultSet) set;
+        final Jdbc4ResultSet pgSet = set.unwrap(Jdbc4ResultSet.class);
         final ResultSetMetaData rsMetaData = pgSet.getMetaData();
 
         final ResultTree tree = new ResultTree();