try to use class loader from Hadoop Configuration

[smartkiwi]

(thread local clas loader) if system class loader fails to find the class.

Apache Spark uploads jars to after Java executor process starts, so they are not available in system class loader.

This PR solves the problem described in this post - allows to use User Defined Predicate classes and objects.

[julienledem]

@smartkiwi what did you think of @rdblue's comment?