Fixing some confusion between 401 vs 403 error code. 401 indicates that the user should attempt to authenticate again. Where as 403 indicates the user is authenticated but not allowed to complete an action. (#804)

Closes #767

lemur/static/app/angular/app.js

@@ -106,7 +106,7 @@
 
       // handle situation where our token has become invalid.
       RestangularConfigurer.setErrorInterceptor(function (response) {
-        if (response.status === 403) {
+        if (response.status === 401) {
           $auth.logout();
           $location.path('/login');
           return false;