don't use 1.im and 0.im

[stevengj]

Use 1im and 0im or 1.0im and 0.0im if you need to enforce a floating-point type (note that e.g. 2.4 + 0im will already promote to Complex{Float64}). The reason is that the 0.im syntax may soon be disallowed in Julia 0.6 (JuliaLang/julia#16339).

[bastikr]

Thank you for the warning. I changed the code accordingly.