Add filter groups for ibuffer

Signed-off-by: Junjie Mao <eternal.n08@gmail.com>
Add auto complete mode

References:
[1] http://cx4a.org/software/auto-complete/
[2] https://github.com/brianjcj/auto-complete-clang
[3] http://blog.csdn.net/winterttr/article/details/7273345

Signed-off-by: Junjie Mao <eternal.n08@gmail.com>