Change donations to contrbutions, add tabbed nav

Introduces components for tabbed navigation and adds a tab menu and item
for non-financial contributions to the donations/contributions page.

config/routes.rb

@@ -15,9 +15,13 @@ Rails.application.routes.draw do
 
   get 'security', to: 'security#index'
 
-  resources :invitations, only: ['index', 'show', 'create', 'destroy']
+  namespace :contributions do
+    root to: 'donations#index'
+    get 'projects', to: 'projects#index'
+    resources :donations, only: ['index']
+  end
 
-  resources :donations
+  resources :invitations, only: ['index', 'show', 'create', 'destroy']
 
   get 'wallet', to: 'wallet#index'
   get 'wallet/transactions', to: 'wallet#transactions'