Temporarily disable parallel builds in travis.
Merge branch 'test-graphics-drawing-commands' into test-graphics-drawing-commands-bis
Fix `drawCircle` signature in `PaintingWindow`.
Change signature of painting commands, update doc, hide functions using Qt objects.
Fix wrong variable name.
Remove obsolete painting function.
Add unit tests for painting commands.
Resorting to ugly hack in order to avoid segfault in Travis.
Revert "Temporarily disable parallel builds in travis."

This reverts commit b9f9d30405547d05788c4de935e2a395b8ed7434.
Merge pull request #78 from DO-CV/test-graphics-drawing-commands-bis

[WIP][MAINT] Add tests for painting commands in Graphics module (bis)