Add keyword argument to `bit_number_measures`

[sbulcsu]

It should be possible to provide a stationary distribution, something like this: function bit_number_measures(P::AbstractMatrix; x=nothing)

[rusandris]

Since bit_number_measures only depend on the stationary distribution x, maybe it would make more sense to get rid of P entirely:

function bit_number_measures(x::Vector{Float64})

 l = -log.(x)
 replace!(l, Inf=>0.0)
 entropy = sum((x .* l)) #C1
 variance =  sum(x .* l .* l) - entropy^2 #C2

 return real(entropy), real(variance), :Success
end

If x is not readily available, one can use bit_number_measures( stationary_distribution(P) )