Added support for local elasticsearch indexed knowledgebase.

I'm not expecting this pull to be accepted, but I wanted to get your opinion on my approach to add a local knowledge-base indexed via an [Elasticsearch](http://www.elasticsearch.org/) daemon, which is checked first before querying Google/Stackoverflow.

I've found myself collecting a lot of answers to questions that either:
1. are very domain-specific or only apply to me
2. might be found online, but in the context of my personal projects, may have a much higher or lower weight than the aggregate found on Stackoverflow

In these cases, it would be useful to maintain a simple locally-maintained knowledge-base of answers where I can easily update answer weights so that they're more applicable to my needs.

The solution I'd been using for a separate project was to keep my questions and answers in a YAML file, and index and retrieve them via Elasticsearch. But of course, this approach doesn't have the breadth of also checking Google. Applying this code to your project merged the best of both worlds for me.