Decide if color values range from 0-255 or 0-1

In the [two](https://github.com/openlayers/ol3/blob/b36eab1dfaf4281d1756ea0eaf7e660b5979d1f0/src/ol/renderer/canvas/canvasmaprenderer.js#L137-L141) [places](https://github.com/openlayers/ol3/commit/f3cace499c82b790efcc37d3dd67935c69f4682c#L5R555) where `ol.Color` is used, there is disagreement about what the range of values should be.  The [docs](https://github.com/openlayers/ol3/blob/e05e0c2f919c26b6106405f83b92adf45897bf2a/src/ol/color.js#L7-L13) suggest 0-255.  Uses in the 2D context's `fillStyle`, `strokeStyle`, and `globalAlpha` along with any CSS use would suggest 0-255 for r/g/b and 0-1 for a.  The 3D context's `clearColor` wants 0-1 for all.