Introducing River functionality

Various pull requests

geo_point support

bug fixes:

* Populate fields aren't stored correctly (Issue #17)
* Date fields aren't being created as dates inside Elasticsearch (Issue #18)
* Models don't index if I create the indexMapping manually (Issue #19)

Enhancements:

* Allow Alternative Index Method (Issue #16)

:feelsgood:

Support for nested fields.

* Dropped 0.4 node support

* package.json fixes

* Fixes event emitter leak with synchronize (Issue #3)

* Allowing host and port to be configured (Issue #11)
* returns full results from elastic search (Issue #10)
* replace _mongodb to instead use mongo id as ES id (Issue #7)
* Extract createMapping as separate method versus doing it behind the scenes.

:shipit: