Miniconda install fails behind firewall. (Conda install launched by IJulia)

Hi,

I have an issue at work where we have a firewall. When I add IJulia, launch jupyterlab and say yes to the Conda install, I have the followig error:

```julia
julia> IJulia.jupyterlab()
install Jupyter via Conda, y/n? [y]: y
[ Info: Downloading miniconda installer ...
┌ Error: Download failed: curl: (7) Failed to connect to repo.continuum.io port 443: Timed out
└ @ Base download.jl:43
ERROR: failed process: Process(`'C:\WINDOWS\System32\curl.exe' -s -S -g -L -f -o 'C:\Users\m.elalaouifaris\.julia\conda\3\installer.exe' https://repo.continuum.io/miniconda/Miniconda3-latest-Windows-x86_64.exe`, ProcessExited(7)) [7]

Stacktrace:
[1] pipeline_error at .\process.jl:525 [inlined]
[2] download_curl(::String, ::String, ::String) at .\download.jl:44
[3] download at .\download.jl:62 [inlined]
[4] _install_conda(::String, ::Bool) at C:\Users\m.elalaouifaris\.julia\packages\Conda\3rPhK\src\Conda.jl:164
[5] _install_conda(::String) at C:\Users\m.elalaouifaris\.julia\packages\Conda\3rPhK\src\Conda.jl:155
[6] runconda(::Cmd, ::String) at C:\Users\m.elalaouifaris\.julia\packages\Conda\3rPhK\src\Conda.jl:112
[7] add(::String, ::String; channel::String) at C:\Users\m.elalaouifaris\.julia\packages\Conda\3rPhK\src\Conda.jl:188
[8] add at C:\Users\m.elalaouifaris\.julia\packages\Conda\3rPhK\src\Conda.jl:187 [inlined] (repeats 2 times)
[9] find_jupyter_subcommand(::String) at C:\Users\m.elalaouifaris\.julia\packages\IJulia\tOM8L\src\jupyter.jl:23
[10] jupyterlab(; dir::String, detached::Bool) at C:\Users\m.elalaouifaris\.julia\packages\IJulia\tOM8L\src\jupyter.jl:108
[11] jupyterlab() at C:\Users\m.elalaouifaris\.julia\packages\IJulia\tOM8L\src\jupyter.jl:107
[12] top-level scope at REPL[4]:1
```

Installing manually minicoda in the right location in .julia folder works.
Is there a way to specify firewall information like what is done with .condarc?

Thanks!
Faris