API stuff

[eric-unc]

Currently testing calling the api locally. There seems to be the following things that need to be done still on the backend:

• send_file I think needs to be imported from flask, I am getting a NameError.
• each api call needs to return something, probably a JSON string, to indicate that the request was successful. Otherwise, on my end, I'm getting status code 500s (that's an error), even though it seems like post-file in the very least definitely works.
• we need to allow more than one person to be able to upload a file at once, or in the very least, we need to put proper restrictions so that trying to upload a file when the server is already working on a file will reject the call.
• the key name should specify the file identifier of the resulting file (so {name}.mid instead of result.mid).
• zip support (I'm not actually sure if it's supported or not?)
• lower priority: we need to make begin_transfer call lstm.py, predict.py in a less hacky way. Currently I don't have all of the dependencies installed, so when these scripts are run, they won't work, but because it's using os.system no errors are returned. I don't know how Python modularization works but it should be looked into.
• lowest priority: on lines 40-41 currently we use os.system to call to unzip the files and to remove the zip files. Using os.system here is platform-dependent (rm -rf won't function on Windows) which is generally bad, there are definitely file utilities built into Python that we could use instead.