Wowza... that's a pretty impressive project to start...
You've gotta record sound, store it, encode it, store it again and send it off to a server over an HTTPS connection (not possible on the spark)
You might be better off having a server in between and having a TCP/UDP connection that your spark records and sends the bytes off to the server... the server would then compile the results and communicate with the Wit API...
I could be far off, someone else with lots more knowledge can help...
If you google anything dealing with recording audio and an arduino, they all rely on a daughter board (shield) with extra hardware to help collect, encode, and store the content as these micro controllers often don't have enough memory.
It relies on an SD board to help and some buffering tricks...
Total inception moment (a post to another post to 3 other posts about it)