Support to use httpsProxy and httpProxy at proxy creation time

Hello,

I'm doing a pull request as you said at #27 

I'm trying to mantain your style. I would prefer to write the if with other format (one line less):
```
urlparams = ""
if params:
    urlparams = "?" + urlencode(params)
```
Thank you
if you want this to be a single line you can right it as `urlparams = "?" + urlencode(params) if params else ""`