Fix request parsing (fixes #60)

[saks]

While investigating issue #60, I found that at times not the entire request body is read after one stream.read call. I noticed that from time to time code was reading only 123 bytes out of 125. Remaining 2 bytes were making request body JSON impossible to parse which has resulted into the error that I've reported in comments for #60.

I also noticed that current implementation does not allow reading requests that are longer than 1024 bytes. I've tried to address it.

Another issue that I found is that even parser status is httparse::Status::Complete, it does not mean that entire body was read already. It should be fixed in proposed PR as well.

It is tricky to automate testing of scenario when not entire request is read in one take, since it's random. Instead I've added a test that ensures that we can parse request that is longer than 1024 bytes.

[lipanski]

@saks this is great, thanks!

Released as 0.15.1

[saks]

thank you @lipanski!