Fix bad exception handling

Signed-off-by: Raul Gutierrez S <rgs@itevenworks.net>
json_count_values: don't report errors and use an exit status

Signed-off-by: Raul Gutierrez S <rgs@itevenworks.net>
json_count_values: support negative top (i.e.: tail results)

Signed-off-by: Raul Gutierrez S <rgs@itevenworks.net>
Release version 0.99.02

Signed-off-by: Raul Gutierrez S <rgs@itevenworks.net>