Use https over git to clone submodules.
Merge pull request #238 from vivekgalatage/patch-1

Use https over git to clone submodules.
Merge pull request #235 from Dparker1990/update_visible_with_delta

Update visible region with insert/erase delta
Ignore dirty submodules

Ignore changes in submodules caused by the build process. This prevents
these submodules from showing up when checking git status.