Transfer operator estimators

[kahaaga]

It would be nice to provide transfer operator-based estimation of entropies too. These are already implemented in PerronFrobenius.jl, but can be greatly simplified and moved here.

• Rectangular-binning based estimator. Straight-forward to include, no additional libraries needed. In progress

• Approximate simplex-based estimator. A bit more cumbersome. Will require dependency on Qhull.jl.

• Exact simplex-based estimator. Depends on Simplices.jl (which depends on PyCall/scipy for access to qhull routines), which makes the package slow. Can be implemented once Simplices.jl is ported to Qhull.jl.

[kahaaga]

Done in #55