Integrate excel parsing into application

[chyku]

Right now the excel parsing script is run separately from the app, so we want that to be integrated into the app before we make the dynamic script parsing changes.

Let me know if this is actually integrated- I can't seem to find it on the frontend.

Blocks #292

[josh-byster]

Some of this gets integrated in #315, where we parse Doodle excel files for scheduling purposes. I definitely agree though that we should have some general management solution for this. For example, as part of my PR, I created a Promise-based binary upload specifically used for Excel file uploads.

const readUploadedFile = inputFile => {
  const reader = new FileReader()

   return new Promise((resolve, reject) => {
    reader.onerror = () => {
      reader.abort()
      reject(new TypeError('Problem encountered while reading input file.'))
    }

     reader.onload = () => {
      resolve(reader.result)
    }
    reader.readAsBinaryString(inputFile)
  })
}

It would be great if we could have these methods encapsulated into some general excel framework within our app.