Add a formula t1.cnf that causes a bug

Signed-off-by: Diego Pasqualin <dpasqualin@c3sl.ufpr.br>
Merge branch 'master' of https://github.com/dpasqualin/d3-dpll
dpll.js: Implement backtracking function

There is still something wrong with t1.cnf..

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