vim: add scala language support

Use vim-scala plugin (with its default mappings disabled) and set up
Syntastic to use the Fast Scala Compiler (FSC).
vim: map <c-x><c-d> to :Dash
vim: disable CtrlP auto <c-p> binding

By default vim binds <c-p> to previous. CtrlP should never override
this, regardless of its name :)
use ctags for scala