Added "open" as a supported image viewer (for OS X)
Added "open" as a supported image viewer (for OS X)

twadleigh/Images.jl,c42f/Images.jl,benmoran/Images.jl,JuliaPackageMirrors/Images.jl,cdsousa/Images.jl,c42f/Images.jl,angi2/Images.jl,zhmz90/Images.jl,benmoran/Images.jl,angi2/Images.jl,twadleigh/Images.jl,zhmz90/Images.jl,timholy/Images.jl,rened/Images.jl,cdsousa/Images.jl,rened/Images.jl