Chains any number of solvers sequentially. Each solver's result becomes
the starting point for the next. Alternative to using %>>% operator.
Examples
if (FALSE) { # \dontrun{
# Three-stage strategy
strategy <- compose(
grid_search(n = 5),
gradient_ascent(max_iter = 50),
newton_raphson(max_iter = 20)
)
result <- strategy(problem, theta0)
} # }