Fixed deprecation warning 
Fixed deprecation warning 

```WARNING: [a] concatenation is deprecated; use collect(a) instead
 in depwarn at deprecated.jl:73
 in oldstyle_vcat_warning at ./abstractarray.jl:29
 in ctranspose at /home/hofmann/.julia/v0.4/Images/src/core.jl:1300```
timholy/Images.jl,JuliaPackageMirrors/Images.jl