increase the tolerance threshold in qutip/tests/test_superop_reps because 1e-12 occationally results in false errors
increase tolerance in expm test in qutip/tests/test_qobj because the previous value 1e-12 has repeatedly been reported to result in false errors on 32 bit systems
explicitly set B operator to superrep choi in choi_to_chi to avoid warning about multiplying superoperators with different represenantations
pep8 compliance
Merge pull request #129 from jrjohansson/fix-super_ops_reps

Fix super ops reps