Sparse Sampler

[Tortar]

e.g. this now fails with OOM:

julia> using DynamicSampling

julia> sampler = DynamicSampler();

julia> push!(sampler, 1, 1.0);

julia> push!(sampler, 10^10, 1.0);
ERROR: OutOfMemoryError()
Stacktrace:
 [1] _growend!
   @ ./array.jl:1072 [inlined]
 [2] resize!
   @ ./array.jl:1315 [inlined]
 [3] resize_w!
   @ ~/.julia/dev/DynamicSampling/src/DynamicWeightedSampler.jl:218 [inlined]
 [4] push!(sp::DynamicSampler{Random.TaskLocalRNG}, idx::Int64, w::Float64)
   @ DynamicSampling ~/.julia/dev/DynamicSampling/src/DynamicWeightedSampler.jl:42
 [5] top-level scope
   @ REPL[4]:1

This option just needs some tweaks though.