Implement HTTP client side timeout

[gjeanmart]

The purpose of this feature is to implement an optional HTTP client side timeout using HttpURLConnection.setReadTimeout(int timeout) because the API Server doesn't provide any timeout mechanism and when java-ipfs-http-client does IPFS.cat(multihash) but the hash cannot be found on the IPFS network, the call hangs forever (or until found). This is usually quite risky and bad practice for a client to block threads like that.

So the idea is to configure a timeout (in ms) to prevent this:

• timeout is set by default to 0 (infinite timeout) to avoid compatibility issues
• timeout can be configured like this:

IPFS ipfs = new IPFS(new MultiAddress("/ip4/127.0.0.1/tcp/5001")).timeout(1000)

[gjeanmart]

PS: A bunch of tests fail but it seems to be the case on master branch as well so I didn't bother fixing it and might give a try in another PR!

[ianopolous]

Thanks! This is a nice improvement