Ol3-Cesium 1.1 release

I am pleased to announce version 1.1 of Ol3-Cesium, based on Ol 3.1.1 and Cesium 1.5.

In addition to bug fixes, it includes the following changes (taken from CHANGES.md)
* Breaking changes
  * The `olFeatureId` has been removed from the picked Cesium counterpart.
    Use directly `olFeature` as illustrated in the synthetic vector examples.
  * The `olcs.OLCesium` constructor signature has changed. Use
    `new olcs.OLCesium({map: map, target: target});` instead of `new olcs.OLCesium(map, target);`
* Custom synchronizer function may be passed to the OLCesium constructor
* Core functions for implementing custom 2D-3D transitions à la Google Map
* Store the `ol.Feature` in the Cesium counterpart instead of an id.
  Use `primitive.olFeature` to read it after picking. See the synthetic vector examples.
* Allow 3D warmup while displaying the 2D map

We are now using a monthly schedule, like Cesium and Ol3, with the goal of migrating each month to
the latest version of each project. Versioning policy is similar to Cesium, with a shift: our
1.XX versions are like Cesium bXX. Practical details may be found on
https://github.com/openlayers/ol3-cesium/wiki/Versioning-policy .

If you are attending FOSDEM in Brussels, do not miss my short talk about the project, on Sunday 1st: