Fix improperly named parse_nil_fmt to parse_nilclass_fmt.
Fix improperly named parse_nil_fmt to parse_nilclass_fmt.

Have to use the name of the column type in the name and the name is NilClass,
not Nil.  This method is called by a send call with the method name
constructed from the column type.

ddoherty03/fat_table,ddoherty03/fat_table