add TLS option from Prometheus community

[lucian-vanghele]

I think it's better if we stay in sync with Prometheus community and use their toolkit.

[lucian-vanghele]

@iamseth can you please take a look and maybe approve this PR? I really think it's way better to use sort of standard for all exporters especially in large environments where you need to use lots of them. I also replaced prometheus/common/log - which is deprecated - with github.com/go-kit/kit/log Thanks.

[Yannig]

Everything seems to be fine. I will do some test to check everything is ok.