Fix Git warning

warning: You ran 'git add' with neither '-A (--all)' or '--ignore-removal', 
whose behaviour will change in Git 2.0 with respect to paths you removed. 
Paths like 'Collage-1.1/CoverageReport/CMake/common/cpp/index-sort-f.html'
that are removed from your working tree are ignored with this version of Git.