Change gist-vim to https clone

.gitmodules

@@ -39,7 +39,7 @@
 	url = https://github.com/tbabej/taskwiki
 [submodule ".vim/bundle/gist-vim"]
 	path = .vim/bundle/gist-vim
-	url = git@github.com:mattn/gist-vim.git
+	url = https://github.com/mattn/gist-vim.git
 [submodule ".vim/bundle/vim-tmux-navigator"]
 	path = .vim/bundle/vim-tmux-navigator
 	url = https://github.com/christoomey/vim-tmux-navigator.git