DOT output: sort hash keys explicitly

This fixes a problem with Perl 5.18, where hash keys are returned in
random order.

The test function indirect_calls in t/Analizo/Output/DOT.t file was
changed to accommodate the explicit ordering.

Signed-off-by: Bryan de Holanda <bryan.h.fernandes@hotmail.com>
Signed-off-by: Lucas Kanashiro <lucas-kanashiro@hotmail.com>
Signed-off-by: Macartur de Sousa <macartur.sc@gmail.com>
Signed-off-by: Victor Cotrim <cotrim149@gmail.com>
HACKING: add links about good commit messages