Tuning the performance ~20 times faster by caching InjectionMap instances

I have to process ~10,000 JSON objects returned from a RESTful service. The original version of Vanilla.extract() method took 8.5 seconds and it reached our response limitation requirement.

By using the caching, now it takes only ~0.4 second.
Sorry for the nitpick, but could you please follow the existing code convention and format as:

```
private const injectionMapCache : Dictionary = new Dictionary();
```