Fix crash with wrong template

+ add log filter for use in templates

sitegin/nunjucks.js

@@ -36,7 +36,11 @@ env.addFilter('paginationList', function(page, count) {
 });
 
 env.addFilter('inspect', function(obj) {
-    return util.inspect(obj);
+  return util.inspect(obj);
+});
+
+env.addFilter('log', function(obj) {
+  return console.log(obj);
 });
 
 env.addFilter('relURL', function(filename, dir){
@@ -53,6 +57,13 @@ module.exports = function(data, type) {
       resolve(tmpl);
     });
   }).then(function(tmpl) {
-    return tmpl.render(data);
+    return new Promise(function(resolve, reject){
+      tmpl.render(data, function(err, val) {
+        if(err) {
+          reject(err);
+        }
+        resolve(val);
+      });
+    })
   });
 }