dpll.js: Fix third node on root problem
graph.js: Switch from cluster layout to tree layout

Using tree layout we have all nodes on same depth put side by side on the
graph

Signed-off-by: Diego Giovane Pasqualin <dpasqualin@c3sl.ufpr.br>
Add t3.cnf, an unsat formula

The graph was suppose to show unsat on every node, but it is showing only on
the last one

Signed-off-by: Diego Giovane Pasqualin <dpasqualin@c3sl.ufpr.br>