Finally clean up `anx--send-request'!
Moved field extraction code into `anx-docgen.el', along with keybindings.

Also relocated `anx--pop-up-buffer' within the file.
Renamed to `anx-api.el'.
Changes to group name, etc., due to having renamed file.
Update `anx-browse-api-docs' to work cross-platform.
Finish TODO item, add another.
Put response buffers in Lisp mode (again).
Add command to save buffer contents, and a DELETE call.

Sort of gross and duplicative, needs cleanup...
Added to TODO
Add TODO item.