Modify some plugin configuration in vimrc.

Fugitive seems to be unstable only with nerdtree, so add it without
nerdtree.
Multiple-cursors is slower choice than vim's built-in functions.
Vim-sbt is also abolished because sbt files should be dealed as scala
files in some reason.
Add ycm plugin to .vim directory.

In my first opinion, ycm should be in other local directory because the
way of building it depends on OS type.
But that opinion is meaningless since I started to manage dotfiles in
Github.
Add delimitMate plugin in vimrc.

It enables you to save the time to add close brackets.
Fix ultisnips directory in vimrc.

YCM is moved to global vim directory, so it is moved too.