`RateSystem` for `CoupledSDEs`

[oameye]

I believe that if we use the use multiple dispatch functionality of Julia, we could essentially write two versions of the apply_ramping function, one where we require auto_sys::CoupledODEs and return nonauto_sys = CoupledODEs(prob, auto_sys.diffeq), and another where we require auto_sys::CoupledSDEs and return nonauto_sys = CoupledSDEs(prob, auto_sys.diffeq). The lines f(u, p, t) = modified_drift( u, p, t, auto_sys, rp.λ, rp.t_start, rp.t_end, rp.r; kwargs... ) and prob = remake(auto_sys.integ.sol.prob; f, p=rp.p_lambda, tspan=(t0, Inf)) should apply to both CoupledODEs and CoupledSDEs, since I believe the function remake can apply to both CoupledODEs and CoupledSDEs.

Originally posted by @ryandeeley in #117 (comment)