Add tests and timeouts to TCP+SNI proxy

[magiconair]

The TCP+SNI proxy needs configurable timeouts and integration tests.

This needs to include a test for #177 which uses the TCP+SNI proxy behind an HAProxy with PROXY protocol enabled (e.g. Amazon AWS ELB)

[magiconair]

I have a test framework for TCP proxies in the release-branch-1.4 and plan to add an integration test for the PROXY protocol. ReadTimeout and WriteTimeout are now honored but that still needs testing.

[magiconair]

merged to master