Refactor Project API to reflect changes upstream

projectile-project-root no longer returns `default-directory` if not in
a project (it returns nil). As such, doom-project-* functions (and their
uses) have been refactored.

+ doom-project-p & doom-project-root are aliases for
  projectile-project-p & projectile-project-root.
+ doom-project-{p,root,name,expand} now has a DIR argument (for
  consistency, since projectile-project-name and
  projectile-project-expand do not).
+ The nocache parameter is no longer necessary, as projectile's caching
  behavior is now more sane.
+ Removed some projectile advice/hacks that are no longer necessary.
+ Updated unit tests

modules/ui/neotree/autoload.el

@@ -8,7 +8,7 @@
 (defun +neotree/open ()
   "Open the neotree window in the current project."
   (interactive)
-  (let ((project-root (doom-project-root 'nocache)))
+  (let ((project-root (doom-project-root)))
     (require 'neotree)
     (if (neo-global--window-exists-p)
         (neotree-hide)
@@ -19,7 +19,7 @@
   "Open the neotree window in the current project, and find the current file."
   (interactive)
   (let ((path buffer-file-name)
-        (project-root (doom-project-root 'nocache)))
+        (project-root (doom-project-root)))
     (require 'neotree)
     (cond ((and (neo-global--window-exists-p)
                 (get-buffer-window neo-buffer-name t))