README: move "custom branch" part to "Basic use"
tree0095bc6683db0a8eccb878e21b3e350f55b70e84
-rw-r--r-- 10014 README_gitrepo.txt
-rwxr-xr-x 1628 git-merge-vim-runtime.sh
-rwxr-xr-x 1129 update-vim-runtime.sh
-rwxr-xr-x 2574 update-vim.sh