WIP : Implementing --no-proxy to not use proxy

This is an almost complete attempt to fix #149 (closed)

wget2 now works with --proxy option. wget2 also works without --proxy option but proxy been set in environment (default behavior)

Last thing remaining is to check for the inverted value of proxy in the case of --no-proxy as currently even with --no-proxy wget2 fetches web-page over proxy.

This commit doesn't include tests. I'll write them once I finish the last bit.