Avoid deadlock on data bigger than buffer by chunking

[emhane]

A deadlock occurs when the data to send is bigger than the available buffer. Chunking data removes this deadlock.

[KolbyML]

For tracking this is an alternative proposed solution to to #61. Details of the bug can be found here #56 .

[KolbyML]

#65 (comment)

This is why I made the PR for this problem #61 . Cause fixing the problem at a deeper level requires a refactor, unless you increase complexity which is what your proposal proposes. Which I guess is fine temporary.

The refactor would be something like combining pending_writes and send_buf into one, since having them both is quite redundant since we already have an outgoing buffer which is sent_packets.packets packets should be renamed to outgoing_buffer to better represent the reference implementations

[KolbyML]

If we choose your temporary solution over mine, you should add a TODO to this PR of.

// todo: combine pending_writes and send_buf

I will rename sent_packets.packets in my overflow fix PR's