tests: travis test failure fix

* Fixes issue in Travis test failures (closes #57)

Signed-off-by: Lars Holm Nielsen <lars.holm.nielsen@cern.ch>
previewer: d3js csv previewer

* Enables CSV file previewer based on d3.js. (closes #36)

Signed-off-by: Lars Holm Nielsen <lars.holm.nielsen@cern.ch>