added solis-wets style step length adaptation
added solis-wets style step length adaptation

JuliaPackageMirrors/BlackBoxOptim.jl,multidis/BlackBoxOptim.jl,tkelman/BlackBoxOptim.jl,tkelman/BlackBoxOptim.jl,tkelman/BlackBoxOptim.jl,multidis/BlackBoxOptim.jl,multidis/BlackBoxOptim.jl,JuliaPackageMirrors/BlackBoxOptim.jl,JuliaPackageMirrors/BlackBoxOptim.jl