Add support for consistent color labels for sparse labels.
Test whether labels are left alone in label2rgb.
Merge pull request #6 from stefanv/tonysyu-consistent-color-labels

Test whether labels are left alone in label2rgb.
Merge pull request #769 from tonysyu/consistent-color-labels

Add support for consistent color labels for sparse labels.
Fix: input label array was being modified if it contained negative labels.