[Vimrc] Add a few plugins

We add a few plugins.
1. Re-enable vim-airline since it now works!
2. szw/vim-ctrlspace for nice buffer management
3. Yggdroot/indentLine for nice indentation lines
4. Remove ctags.vim since tagbar provides the functionality in airline

Also set some airline variables
[vimrc] Add hardmode and disable arrow keys. Lets break the habits!