Refactored Rendering code out to it's own folder under root.

Also renamed .histogram to .tileHistograms, and made a
.histogram that converges, since

```scala
val breaks =
  layerNames
    .zip(weightValues)
    .map { case (name,weight) =>
      RasterSource(name,re) * weight
     }
    .reduce(_+_)
    .histogram
    .converge
    .map(_.getQuantileBreaks(numBreaks))
    .map { breaks =>
    val breaksArray = breaks.mkString("[", ",", "]")
    s"""{ "classBreaks" : $breaksArray }"""
  }
```

feels unnatural to have a converge in there, where

```scala
val breaks =
  layerNames
    .zip(weightValues)
    .map { case (name,weight) =>
      RasterSource(name,re) * weight
     }
    .reduce(_+_)
    .histogram
    .map(_.getQuantileBreaks(numBreaks))
    .map { breaks =>
    val breaksArray = breaks.mkString("[", ",", "]")
    s"""{ "classBreaks" : $breaksArray }"""
  }
```

seems more natural of an API.

This means to get means over tiles or something like that, you would do:

```scala
val breaks =
  RasterSource("layerName")
    .tileHistograms
    .map(_.mean)
    .reduce(_*_)
```

not that the actual result of that example would be useful.
changing spark project's name to be consistent with other sub-projects
added sbteclipse plugin
added basic tiling scheme
added some comments
more comments
removed sbteclipse plugin as it makes more sense to add it to local .sbt/plugins
Merge remote-tracking branch 'upstream/master' into hydrology
rewrote zoom to have early returns for sake of readability
Merge pull request #648 from ameetkini/tileid-scheme

TMS tiling scheme
Merge remote-tracking branch 'upstream/master' into rendering-namespace
Fixes 'dev' project.
Merge pull request #649 from lossyrob/rendering-namespace

Refactored Rendering code out to it's own folder under root.
Upgrade akka to 2.2.3
Merge pull request #650 from lossyrob/akka-upgrade

Upgrade akka to 2.2.3
Merge branch 'hydrology' of https://github.com/Markko/geotrellis into hydrology
Fix to io.LoadTile for loading raster extent
Changed raster loading by name to accept data store name.

- If a layer is requested by only name (no data store name specified) and there is more than one data store that has a raster layer by that name an exception is thrown saying so.
Merge pull request #652 from lossyrob/loadtile-rasterextent

Fix to io.LoadTile for loading raster extent
Merged in upstream fix to LoadTile.