Adds basic Requests library

[chuckha]

With a fixed history.

[despeset]

• requests.jl should probably be src/Requests.jl
• HttpMethodBitmaskToName(method) on line 27 needs to be HttpMethodBitmaskToName[method]
• request("http://google.com") seems to return the DNS response, it should be followed.
• request("http://www.google.com") fails with the below error – see the Julia issue about getaddrinfo

ERROR: getaddrinfo callback: no such file or directory (ENOENT)
 in _uv_hook_getaddrinfo at socket.jl:201
 in process_events at stream.jl:312
 in event_loop at multi.jl:1381
 in anonymous at client.jl:284