Fixed console.warning is not a function.

```
TypeError: console.warning is not a function
    at /opt/ping-api/node_modules/enju/lib/query.js:165:25
    at <anonymous>:null:null
    at process._tickDomainCallback (internal/process/next_tick.js:228:7)
```

Author: kelp404

lib/query.js

@@ -162,7 +162,7 @@
               property = referenceProperties[l];
               resolveDocument = dataTable[property.referenceClass.name][document[property.propertyName]];
               if (property.required && !resolveDocument) {
-                console.warning(`There are a reference class can't mapping: ${property.referenceClass.name}::${document[property.propertyName]}`);
+                console.log(`There are a reference class can't mapping: ${property.referenceClass.name}::${document[property.propertyName]}`);
                 continue;
               }
               document[property.propertyName] = resolveDocument;

src/lib/query.coffee

@@ -108,7 +108,7 @@ module.exports = class Query
                 for property in referenceProperties  # loop all reference properties in the document
                     resolveDocument = dataTable[property.referenceClass.name][document[property.propertyName]]
                     if property.required and not resolveDocument
-                        console.warning("There are a reference class can't mapping: #{property.referenceClass.name}::#{document[property.propertyName]}")
+                        console.log "There are a reference class can't mapping: #{property.referenceClass.name}::#{document[property.propertyName]}"
                         continue
                     document[property.propertyName] = resolveDocument
             resolve()