[Fix #803] Add eval-sexp-fu

The package is lightweight enough that the load time is negligible. For
simplicity, just use it directly.

spacemacs/packages.el

@@ -32,6 +32,7 @@
     ediff
     elisp-slime-nav
     eldoc
+    eval-sexp-fu
     evil
     evil-anzu
     evil-args
@@ -551,6 +552,9 @@ which require an initialization must be listed explicitly in the list.")
     (progn
       (spacemacs|hide-lighter eldoc-mode))))
 
+(defun spacemacs/init-eval-sexp-fu ()
+  (use-package eval-sexp-fu))
+
 (defun spacemacs/init-evil ()
   (use-package evil
     :init