Cannot read complex numbers

[nhz2]

There is a bug in how complex numbers are being read.

Here is an example:

julia> using Zarr

julia> p = tempname()
"/tmp/jl_GLajCLonen"

julia> z1 = zcreate(Complex{Float32}, 10,10,path = p,chunks=(10, 10))
ZArray{ComplexF32} of size 10 x 10

julia> z1 .= 42f0*im
ZArray{ComplexF32} of size 10 x 10

julia> z2 = zopen(p)
ZArray{ComplexF64} of size 10 x 10

julia> z1[:,:] == z2[:,:]
false

julia> using JSON

julia> JSON.parsefile(joinpath(p, ".zarray"))["dtype"]
"<c8"

The "dtype" of the array is "<c8", so it is a complex number with a total of 8 bytes, or Complex{Float32} in Julia, but is getting incorrectly read as Complex{Float64}

This issue is fixed by PR #181