Ignore broken certificates when using n over ssl proxy

[alqu]

In wget there is already the "--no-check-certificate" option, but in curl it was missing. Added.

Pull Request Template:

Describe what you did

I added an additional param for curl that ignores invalid ssl certificates. Otherwise, the download fails and leaves a broken install behind.

How you did it

I tried to pull a newer version of node with n latest through an ssl proxy. Curl was complaining that the certificate was not valid - which is true for SSL proxies a.k.a. MITM.

How to verify it doesn't effect the functionality of n

Fetching updates with a "normal" environment works flawlessly.

[dskrvk]

This shouldn't be enabled by default in either place (#475 removes the option for wget). If some users absolutely need this and are OK with sacrificing security, there can be an option to skip certificate checks.

[dskrvk]

Actually, the same change has already been submitted and received a similar comment in #324.

[shadowspawn]

Proxy setup is a bit tricky @alqu, but as noted by @dskrvk the default for curl and wget should be secure.

[alqu]

Thanks!

Meanwhile, this feature request is not that urgent nor valid anymore, so I am fine with it.