Add array type for storing coordinate values to allow improving accuracy for small radius

[ewelinaBS]

For small radius <~50cm, the clustering is not accurate. (Probably the accuracy will be different depending on the latitude.) The problem originates from rounding the coordinates to float32.

Work done

Enable arrayType argument for supercluster constructor to determine in what format store the coordinates values.
Default Float32Array value will work the same as before.

[andrewharvey]

I've added a unit test for this in #249

[klyakh]

I had to switch back to GridAlgorithm instead of SuperClusterAlgorithm. I have situations where many markers are on the same building with almost the same position. So when user zooms in to 20 or above, clusters become problematic:

• some very close markers are not clustered, even though they are on almost the same position
• some clusters have standalone markers very close to them, basically overlapping with cluster marker; they should be included in the cluster.

[mourner]

This should be resolved by #258