Change the way the Elastica_Search object is created

This way we will have more flexibility to modify the search.
We will be able to support multiple index, multi-types and others.
Add a filter to modify the search

Will be able to use all the Elastica_Search API.
Merge pull request #15 from turcottedanny/search_multiple_index

Ability to modify Elastica_Search criteria through API before execution.