Projection can be defined as string, witch allow to define custom projection with ol.proj.addProjection, by the way EPSG:4326 and EPSG:3857 are already defined bu default in ol3 http://openlayers.org/en/master/apidoc/ol.proj.Projection.html
Merge pull request #14 from Geode/CustomProjection

Projection can be defined as string, witch allow to define custom projec...