Fix Julia 0.5 Travis warnings and errors

[anriseth]

WARNING: Method definition objective(Any) in module HJBSolver at /home/travis/.julia/v0.5/HJBSolver/src/policyiteration.jl:46 overwritten at /home/travis/.julia/v0.5/HJBSolver/src/policyiteration.jl:62.
WARNING: Method definition objective(Any) in module HJBSolver at /home/travis/.julia/v0.5/HJBSolver/src/policyiteration.jl:62 overwritten at /home/travis/.julia/v0.5/HJBSolver/src/policyiteration.jl:86.
Constant policy approximation, Merton
WARNING: could not attach metadata for @simd loop.
 82.104381 seconds (416.48 M allocations: 12.671 GB, 1.27% gc time)
2 facts verified.
Policy iteration, Merton
ERROR: LoadError: LoadError: UndefVarError: hamiltonian not defined
 in updatepol!(::Array{Float64,1}, ::Array{Float64,1}, ::HJBSolver.HJBOneDim{Float64}, ::Float64, ::LinSpace{Float64}, ::Float64) at /home/travis/.julia/v0.5/HJBSolver/src/policyiteration.jl:45