Merge pull request #1 from Ryman/master

Better error handling
Added support for SOCKS4
Update README.md
Update README.md
Update socks4.rs
Update README.md
Minor adjustments
Fixed a mistake I made
Added Socks5 support
Update README.md
Add gitignore.
Remove trailing whitespace.
Fail for unhandled cases.
Fix warnings.
Handle different address types from server.
Accept Domain/Ipv4/Ipv6 destinations.
Extract io_err to util module.
Reexport for convenience
Add basic tests