Changed the regexp rule for TodoDate to make to be compatible with todo.sh
README: Added the description about <leader>-D
Merge pull request #4 from seiichi/todosh-complatible-date-format

Changed the regexp rule for TodoDate to make to be compatible with todo.sh
Merge pull request #5 from seiichi/add-missing-leader-D-to-readme

README: Added the description about <leader>-D