Add a very basic calendar to vim

This calendar may help me to organize my vimwiki better since they are
very well integrated into each other. So it can help me to manage my
diary and organize some basic stuff.

.vimrc

@@ -76,6 +76,9 @@ Plugin 'git@github.com:mattn/emmet-vim.git'
 " Add a status/tabline at the bottom
 Plugin 'git@github.com:vim-airline/vim-airline.git'
 
+" A calendar-integration
+Plugin 'git@github.com:mattn/calendar-vim.git'
+
 call vundle#end()
 " End: Manage plugins
 filetype plugin on