introduced the QueryExecutor strategy in order to move the default implementation of StdCouchDbConnector.executeQuery(ViewQuery, ResponseCallback) to new class DefaultQueryExecutor that is used by default. This should greatly improve the ability to change the default behavior in a non intrusive way
extracted method buildQueryURI() so that future QueryExecutor implementations can get the URI object and eventually change it before turning it into a String
Alternative implementations of QueryExecutor may need accessor on keys
Merge pull request #174 from YannRobert/IntroduceQueryExecutorStrategy

Introduce query executor strategy, enabling #165