Built time tests sometimes fail

[olebole]

Sometimes the build time tests fail during compilation. This probably depends on the random seed. Output of the failed test:

 9/14 Test  #9: test_proximal                ***Failed    0.01 sec

test_proximal is a Catch v1.2.0 host application.
Run with -? for options

Randomness seeded to: 1476211399

-------------------------------------------------------------------------------
L1 proximal
  General case
  Positivity constraints
-------------------------------------------------------------------------------
/build/sopt-2.0.0/cpp/tests/proximal.cc:200
...............................................................................

/build/sopt-2.0.0/cpp/tests/proximal.cc:247: FAILED:
  CHECK( (l1.objective(input, p_plus, gamma) > mini or rel_var < l1.tolerance() * 10) )
with expansion:
  false

/build/sopt-2.0.0/cpp/tests/proximal.cc:247: FAILED:
  CHECK( (l1.objective(input, p_plus, gamma) > mini or rel_var < l1.tolerance() * 10) )
with expansion:
  false

/build/sopt-2.0.0/cpp/tests/proximal.cc:258: FAILED:
  CHECK( (l1.objective(input, p_plus, gamma) > mini or rel_var < l1.tolerance() * 10) )
with expansion:
  false

/build/sopt-2.0.0/cpp/tests/proximal.cc:258: FAILED:
  CHECK( (l1.objective(input, p_plus, gamma) > mini or rel_var < l1.tolerance() * 10) )
with expansion:
  false

/build/sopt-2.0.0/cpp/tests/proximal.cc:258: FAILED:
  CHECK( (l1.objective(input, p_plus, gamma) > mini or rel_var < l1.tolerance() * 10) )
with expansion:
  false

/build/sopt-2.0.0/cpp/tests/proximal.cc:258: FAILED:
  CHECK( (l1.objective(input, p_plus, gamma) > mini or rel_var < l1.tolerance() * 10) )
with expansion:
  false

===============================================================================
test cases:   7 |   6 passed | 1 failed
assertions: 276 | 270 passed | 6 failed

I also had a test failure in test 14, but didn't save the output.