1. Dotfile

It is now possible to reload the dotfile and layers anywhere with `SPC f e
R`. This key binding *replaces* the old `C-c C-c` and `SPC m c c` only
available in the dotfile.

*Important* You should replace your `(defvar <layer>-packages ...)`,
`(defvar <layer>-pre-extensions ...)`, `(defvar <layer>-post-extensions ...)`
and `(defvar <layer>-excluded-packages ...)` by `(setq ...)`. This will
allow to install newly added packages to a layer without restarting spacemacs
by pressing `SPC f e R`. Be sure to remove the docstring when replacing the
`defvar` since `setq` does not take a third argument. 

`:variables` keyword now behaves like a regular `setq` so you'll have to
quote any value appropriately.

2. Emacs lisp and Shell config are now in their own layers

Be sure to add the new layers `emacs-lisp` and `shell` to your dotfile to
continue to enjoy the emacs-lisp and shell configurations of Spacemacs.

Also be sure to check the key binding `SPC '` to open a shell buffer.

3. Key bindings

`SPC b s` to switch buffer is now on `SPC b b`.
`SPC f f` uses helm instead of ido, set the new variable.
`dotspacemacs-use-ido` to t to get back the old ido behavior.
`TAB` and `C-z` in helm buffers have been *swapped*.

4. Sentence delimiter

Sentence delimiter is now a *single space* as opposed to Emacs default
which is double spaces.