First working version of drakma-async client finished

Since my previous HTTP client update I’ve made a good amount of progress. I created an HTTP parser entirely in lisp that is able to determine the readiness of an HTTP response. It supports content-length and chunking response types. It does not currently check for 100 Continue responses yet, but once it does, I think it will be complete.

Note that the drakma-async project requires cl-async’s future+stream branch to work.

So the general workflow is as such:

1. Init http-client-stream, send request into returned stream. If doing this through drakma-async, a future is returned, which will be triggered when the request completes.
2. Wait for data on the socket. Once data comes in from the server, we remove it from the socket and pass it into the HTTP parser, which stores it internally and checks if the response is complete.
3. If the response is not complete, we wait for the next round of data to come in. If the response is complete, we take the data stored in the HTTP parser and shove it back into the beginning of the original socket stream. We then pass that stream (containing all the data from the complete response) into drakma-async, which parses the stream just like drakma does normally.
4. The future drakma-async returned is finished with the values normally passed back from drakma, and the calling application can attach a callback to get the results.

From my initial testing, this is working wonderfully. Aside from any unknown bugs in the HTTP parser, the only case not being handled is 100 Continue being passed back from the server. Otherwise, drakma-async is now in beta.