Fail-fast on too-big request sizes when possible

[nicmunroe]

Following on to issue #27, we should fail-fast when the request has a content-length greater than the configured max-allowed-request-size value. Currently the failure only happens after we've actually received enough bytes to go over the threshold. This change cannot affect chunked encoding requests since they don't include a content-length header.

[blling]

Netty4.1 "New and Noteworthy" documented a improvement:
Better oversized message handling with HttpObjectAggregator

In 4.0, there was no way to reject an oversized HTTP message before a client sends the content even if 100-continue header was present.

This release adds an overridable method called handleOversizedMessage so that a user can perform his or her preferred task. By default, it responds with '413 Request Entity Too Large' response and closed the connection

Should this be helpful for no content-length case?
And any plans to update to netty 4.1?

[nicmunroe]

@vicbevis Riposte doesn't use HttpObjectAggregator for various reasons (mainly support for chunk-streaming for ProxyRouterEndpoints so we don't have to pull in the full payload, but other reasons as well), so that unfortunately doesn't help.

[rabeyta]

fixed in 0.10.0