No more DomainErrors in Julia

Use JuliaMath/NaNMath.jl.

sqrt(x), log(x), and pow(x) will throw DomainError exceptions with negative x, interrupting differential equation solvers. One can use these functions' counterparts in JuliaMath/NaNMath.jl, returning NaN instead of throwing a DomainError. Then, the solvers will reject the solution and retry with a smaller time step.

sqrt(-1.0) # throws DomainError

import NaNMath as nm
nm.sqrt(-1.0) # NaN